Blue is one of the three

primary colours A set of primary colors or primary colours (see spelling differences) consists of colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used to create the perception of a b ...

in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between

violet Violet may refer to: Common meanings * Violet (color), a spectral color with wavelengths shorter than blue * One of a list of plants known as violet, particularly: ** ''Viola'' (plant), a genus of flowering plants Places United States * Viol ...

and cyan on the

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors ...

visible light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...

. The eye perceives blue when observing light with a

dominant wavelength In color science, the dominant wavelength is a method of characterizing a color's hue. Along with purity, it makes up one half of the Helmholtz coordinates. A color's dominant wavelength is the wavelength of monochromatic spectral light that evo ...

between approximately 450 and 495 nanometres. Most blues contain a slight mixture of other colours; azure contains some green, while

ultramarine Ultramarine is a deep blue color pigment which was originally made by grinding lapis lazuli into a powder. The name comes from the Latin ''ultramarinus'', literally 'beyond the sea', because the pigment was imported into Europe from mines in Afg ...

contains some violet. The clear daytime sky and the deep sea appear blue because of an optical effect known as

Rayleigh scattering Rayleigh scattering ( ), named after the 19th-century British physicist Lord Rayleigh (John William Strutt), is the predominantly elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of th ...

. An optical effect called

Tyndall effect The Tyndall effect is light scattering by particles in a colloid or in a very fine suspension. Also known as Tyndall scattering, it is similar to Rayleigh scattering, in that the intensity of the scattered light is inversely proportional to ...

explains

blue eyes Eye color is a polygenic phenotypic character determined by two distinct factors: the pigmentation of the eye's iris and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris. In humans, the p ...

. Distant objects appear more blue because of another optical effect called aerial perspective. Blue has been an important colour in art and decoration since ancient times. The semi-precious stone lapis lazuli was used in ancient Egypt for jewellery and ornament and later, in the

Renaissance The Renaissance ( , ) , from , with the same meanings. is a period in European history The history of Europe is traditionally divided into four time periods: prehistoric Europe (prior to about 800 BC), classical antiquity (800 BC to AD ...

, to make the pigment

, the most expensive of all pigments. In the eighth century Chinese artists used cobalt blue to colour fine blue and white porcelain. In the

Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire ...

, European artists used it in the windows of

cathedral A cathedral is a church that contains the '' cathedra'' () of a bishop, thus serving as the central church of a diocese, conference, or episcopate. Churches with the function of "cathedral" are usually specific to those Christian denominatio ...

s. Europeans wore clothing coloured with the vegetable dye

woad ''Isatis tinctoria'', also called woad (), dyer's woad, or glastum, is a flowering plant in the family Brassicaceae (the mustard family) with a documented history of use as a blue dye and medicinal plant. Its genus name, Isatis, derives from ...

until it was replaced by the finer

indigo Indigo is a deep color close to the color wheel blue (a primary color in the RGB color space), as well as to some variants of ultramarine, based on the ancient dye of the same name. The word "indigo" comes from the Latin word ''indicum'', m ...

from America. In the 19th century, synthetic blue dyes and pigments gradually replaced organic dyes and mineral pigments. Dark blue became a common colour for military uniforms and later, in the late 20th century, for business suits. Because blue has commonly been associated with harmony, it was chosen as the colour of the flags of the

United Nations The United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmoniz ...

and the

European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been de ...

. Surveys in the US and Europe show that blue is the colour most commonly associated with harmony, faithfulness, confidence, distance, infinity, the imagination, cold, and occasionally with sadness. In US and European public opinion polls it is the most popular colour, chosen by almost half of both men and women as their favourite colour. The same surveys also showed that blue was the colour most associated with the masculine, just ahead of black, and was also the colour most associated with intelligence, knowledge, calm, and concentration.

Etymology and linguistics

The modern English word ''blue'' comes from

Middle English Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments following the Old English ...

or , from the

Old French Old French (, , ; Modern French: ) was the language spoken in most of the northern half of France from approximately the 8th to the 14th centuries. Rather than a unified language, Old French was a linkage of Romance dialects, mutually intellig ...

, a word of Germanic origin, related to the

Old High German Old High German (OHG; german: Althochdeutsch (Ahd.)) is the earliest stage of the German language, conventionally covering the period from around 750 to 1050. There is no standardised or supra-regional form of German at this period, and Old High ...

word (meaning 'shimmering, lustrous').''Webster's Seventh New Collegiate Dictionary'' (1970). In heraldry, the word '' azure'' is used for ''blue''. In

Russian Russian(s) refers to anything related to Russia, including: *Russians (, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *Rossiyane (), Russian language term for all citizens and peo ...

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...

and some other languages, there is no single word for blue, but rather different words for light blue (, ; ) and dark blue (, ; ). See

Colour term A color term (or color name) is a word or phrase that refers to a specific color. The color term may refer to human perception of that color (which is affected by visual context) which is usually defined according to the Munsell color system, or t ...

. Several languages, including

Japanese Japanese may refer to: * Something from or related to Japan, an island country in East Asia * Japanese language, spoken mainly in Japan * Japanese people, the ethnic group that identifies with Japan through ancestry or culture ** Japanese diaspor ...

and Lakota Sioux, use the same word to describe blue and green. For example, in

Vietnamese Vietnamese may refer to: * Something of, from, or related to Vietnam, a country in Southeast Asia ** A citizen of Vietnam. See Demographics of Vietnam. * Vietnamese people, or Kinh people, a Southeast Asian ethnic group native to Vietnam ** Overse ...

, the colour of both tree leaves and the sky is . In Japanese, the word for blue (, ) is often used for colours that English speakers would refer to as green, such as the colour of a

traffic signal Traffic lights, traffic signals, or stoplights – known also as robots in South Africa are signalling devices positioned at road intersections, pedestrian crossings, and other locations in order to control flows of traffic. Traffic lights ...

meaning "go". In Lakota, the word is used for both blue and green, the two colours not being distinguished in older Lakota. (For more on this subject, see

Distinguishing blue from green in language The ruling made by the judge or panel of judges must be based on the evidence at hand and the standard binding precedents covering the subject-matter (they must be ''followed''). Definition In law, to distinguish a case means a court decides th ...

.) Linguistic research indicates that languages do not begin by having a word for the colour blue. Colour names often developed individually in natural languages, typically beginning with

black Black is a color which results from the absence or complete absorption of visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white ...

and

white White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White o ...

(or dark and light), and then adding

red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...

, and only much later – usually as the last main category of colour accepted in a language – adding the colour blue, probably when blue pigments could be manufactured reliably in the culture using that language.

Optics and colour theory

Human eyes perceive blue when observing light which has a

of roughly 450–495 nanometres. Blues with a higher frequency and thus a shorter wavelength gradually look more violet, while those with a lower frequency and a longer wavelength gradually appear more green. Pure blue, in the middle, has a wavelength of 470 nanometres.

Isaac Newton Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, alchemist, theologian, and author (described in his time as a " natural philosopher"), widely recognised as one of the grea ...

included blue as one of the seven colours in his first description the

visible spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' or simply light. A typical human eye will respond to wa ...

. He chose seven colours because that was the number of notes in the musical scale, which he believed was related to the optical spectrum. He included

, the hue between blue and violet, as one of the separate colours, though today it is usually considered a hue of blue. In painting and traditional

colour theory In the visual arts, color theory is the body of practical guidance for color mixing and the visual effects of a specific color combination. Color terminology based on the color wheel and its geometry separates colors into primary color, seconda ...

, blue is one of the three

of pigments (red, yellow, blue), which can be mixed to form a wide

gamut In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain ''complete subset'' of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circ ...

of colours. Red and blue mixed together form violet, blue and yellow together form green. Mixing all three primary colours together produces a dark brown. From the Renaissance onward, painters used this system to create their colours. (See RYB colour model.) The RYB model was used for

colour printing Color printing or colour printing is the reproduction of an image or text in color (as opposed to simpler black and white or monochrome printing). Any natural scene or color photograph can be optically and physiologically dissected into three ...

Jacob Christoph Le Blon Jacob Christoph Le Blon, or Jakob Christoffel Le Blon, (2 May 1667 – 16 May 1741) was a painter and engraver from Frankfurt who invented the system of three- and four-colour printing, using an RYB color model which segued into the modern CMY ...

as early as 1725. Later, printers discovered that more accurate colours could be created by using combinations of cyan, magenta, yellow, and black ink, put onto separate inked plates and then overlaid one at a time onto paper. This method could produce almost all the colours in the

with reasonable accuracy. File:AdditiveColorMixing.svg, Additive colour mixing. The combination of

primary colour A set of primary colors or primary colours (see spelling differences) consists of colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used to create the perception of a bro ...

s produces secondary colours where two overlap; the combination red, green, and blue each in full intensity makes white. File:Closeup of pixels.JPG, Red, green, and blue subpixels on an LCD display. On the HSV colour wheel, the

complement A complement is something that completes something else. Complement may refer specifically to: The arts * Complement (music), an interval that, when added to another, spans an octave ** Aggregate complementation, the separation of pitch-clas ...

of blue is

yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In the ...

; that is, a colour corresponding to an equal mixture of

and

green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a combi ...

light. On a colour wheel based on traditional colour theory ( RYB) where blue was considered a primary colour, its complementary colour is considered to be

orange Orange most often refers to: *Orange (fruit), the fruit of the tree species '' Citrus'' × ''sinensis'' ** Orange blossom, its fragrant flower *Orange (colour), from the color of an orange, occurs between red and yellow in the visible spectrum * ...

(based on the Munsell colour wheel).

Laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fi ...

s emitting in the blue region of the spectrum became widely available to the public in 2010 with the release of inexpensive high-powered 445–447 nm

laser diode The laser diode chip removed and placed on the eye of a needle for scale A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with e ...

technology. Previously the blue wavelengths were accessible only through DPSS which are comparatively expensive and inefficient, but still widely used by scientists for applications including

optogenetics Optogenetics is a biological technique to control the activity of neurons or other cell types with light. This is achieved by expression of light-sensitive ion channels, pumps or enzymes specifically in the target cells. On the level of individ ...

, Raman spectroscopy, and particle image velocimetry, due to their superior beam quality. Blue

gas laser A gas laser is a laser in which an electric current is discharged through a gas to produce coherent light. The gas laser was the first continuous-light laser and the first laser to operate on the principle of converting electrical energy to a lase ...

s are also still commonly used for

holography Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other applications. In principle, i ...

, DNA sequencing, optical pumping, among other scientific and medical applications.

Shades and variations

Blue is the colour of light between

and cyan on the

. Hues of blue include indigo and

, closer to violet; pure blue, without any mixture of other colours; Azure, which is a lighter shade of blue, similar to the colour of the sky; Cyan, which is midway in the spectrum between blue and

, and the other blue-greens such as

turquoise Turquoise is an opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminium, with the chemical formula . It is rare and valuable in finer grades and has been prized as a gemstone and ornamental stone for thousands of year ...

teal alt=American teal duck (male), Green-winged teal (male) Teal is a greenish-blue colour. Its name comes from that of a bird — the Eurasian teal (''Anas crecca'') — which presents a similarly coloured stripe on its head. The word is oft ...

, and aquamarine. Blue also varies in shade or tint; darker shades of blue contain black or grey, while lighter tints contain white. Darker shades of blue include ultramarine, cobalt blue,

navy blue Navy blue is a very dark shade of the color blue. Navy blue got its name from the dark blue (contrasted with naval white) worn by officers in the Royal Navy since 1748 and subsequently adopted by other navies around the world. When this color ...

, and

Prussian blue Prussian blue (also known as Berlin blue, Brandenburg blue or, in painting, Parisian or Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula Fe CN)">Cyanide.html" ;"title="e(Cyani ...

; while lighter tints include

sky blue Sky blue is a shade of light blue comparable to that of a clear daytime sky. The term (as "sky blew") is attested from 1681. A 1585 translation of Nicolas de Nicolay's 1576 ''Les navigations, peregrinations et voyages faicts en la Turquie'' i ...

, azure, and

Egyptian blue Egyptian blue, also known as calcium copper silicate (CaCuSi4O10 or CaOCuO(SiO2)4 (calcium copper tetrasilicate)) or cuprorivaite, is a pigment that was used in ancient Egypt for thousands of years. It is considered to be the first synthetic pi ...

. (For a more complete list see the

List of colours These are the lists of colors; * List of colors: A–F * List of colors: G–M * List of colors: N–Z * List of colors (compact) * List of colors by shade * List of color palettes * List of Crayola crayon colors * List of RAL colors * List ...

As a structural colour

In nature, many blue phenomena arise from

structural colouration Structural coloration in animals, and a few plants, is the production of colour by microscopically structured surfaces fine enough to interfere with visible light instead of pigments, although some structural coloration occurs in combination w ...

, the result of interference between reflections from two or more surfaces of

thin films A thin film is a layer of material ranging from fractions of a nanometer ( monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ...

, combined with refraction as light enters and exits such films. The geometry then determines that at certain angles, the light reflected from both surfaces interferes constructively, while at other angles, the light interferes destructively. Diverse colours therefore appear despite the absence of colourants.

Colourants

File:Egyptian blue.jpg,

File:Cobalt Blue.JPG, Cobalt blue. File:Bleu phtalo.jpg,

Copper phthalocyanine Copper phthalocyanine (CuPc), also called phthalocyanine blue, phthalo blue and many other names, is a bright, crystalline, synthetic blue pigment from the group of phthalocyanine dyes. Its brilliant blue is frequently used in paints and dy ...

. File:YInMn_Blue_-_cropped.jpg, YInMn blue. File:Prussian blue.jpg,

, Fe CN).html"_;"title="Cyanide.html"_;"title="e(Cyanide">CN)">Cyanide.html"_;"title="e(Cyanide">CN)_is_the_blue_of_blueprint.html" ;"title="Cyanide">CN).html" ;"title="Cyanide.html" ;"title="e(Cyanide">CN)">Cyanide.html" ;"title="e(Cyanide">CN) is the blue of blueprint">Cyanide">CN).html" ;"title="Cyanide.html" ;"title="e(Cyanide">CN)">Cyanide.html" ;"title="e(Cyanide">CN) is the blue of blueprints.

Artificial blues

, the first artificial pigment, was produced in the third millennium BC in Ancient Egypt. It is produced by heating pulverized sand, copper, and natron. It was used in tomb paintings and funereal objects to protect the dead in their afterlife. Prior to the 1700s, blue colourants for artwork were mainly based on lapis lazuli and the related mineral ultramarine. A breakthrough occurred in 1709 when German druggist and pigment maker Johann Jacob Diesbach discovered

. The new blue arose from experiments involving heating dried blood with iron sulphides and was initially called Berliner Blau. By 1710 it was being used by the French painter

Antoine Watteau Jean-Antoine Watteau (, , ; baptised October 10, 1684died July 18, 1721) Alsavailablevia Oxford Art Online (subscription needed). was a French painter and draughtsman whose brief career spurred the revival of interest in colour and movement, a ...

, and later his successor

Nicolas Lancret Nicolas Lancret (22 January 1690 – 14 September 1743) was a French painter. Born in Paris, he was a brilliant depicter of light comedy which reflected the tastes and manners of French society during the regency of the Duke of Orleans and, late ...

. It became immensely popular for the manufacture of wallpaper, and in the 19th century was widely used by French impressionist painters. Beginning in the 1820s, Prussian blue was imported into Japan through the port of

Nagasaki is the capital and the largest Cities of Japan, city of Nagasaki Prefecture on the island of Kyushu in Japan. It became the sole Nanban trade, port used for trade with the Portuguese and Dutch during the 16th through 19th centuries. The Hi ...

. It was called ''bero-ai'', or Berlin blue, and it became popular because it did not fade like traditional Japanese blue pigment, ''ai-gami'', made from the

dayflower ''Commelina'' is a genus of approximately 170 species commonly called dayflowers due to the short lives of their flowers. They are less often known as widow's tears. It is by far the largest genus of its family, Commelinaceae. The Swedish taxonom ...

. Prussian blue was used by both Hokusai, in his wave paintings, and

Hiroshige Utagawa Hiroshige (, also ; ja, 歌川広重 ), born Andō Tokutarō (; 1797 – 12 October 1858), was a Japanese ''ukiyo-e'' artist, considered the last great master of that tradition. Hiroshige is best known for his horizontal-format l ...

. In 1799 a French chemist,

Louis Jacques Thénard Louis Jacques Thénard (4 May 177721 June 1857) was a French chemist. Life He was born in a farm cottage near Nogent-sur-Seine in the Champagne district the son of a farm worker. In the post-Revolution French educational system , most boys rec ...

, made a synthetic cobalt blue pigment which became immensely popular with painters. In 1824 the Societé pour l'Encouragement d'Industrie in France offered a prize for the invention of an artificial

which could rival the natural colour made from lapis lazuli. The prize was won in 1826 by a chemist named Jean Baptiste Guimet, but he refused to reveal the formula of his colour. In 1828, another scientist,

Christian Gmelin Christian Gottlob Gmelin (12 October 1792 – 13 May 1860) was a German chemist. He was born in Tübingen, Germany, and was a grandson of Johann Konrad Gmelin and a great-grandson of Johann Georg Gmelin. Scientific career In 1818, Gmelin was one ...

then a professor of chemistry in Tübingen, found the process and published his formula. This was the beginning of new industry to manufacture artificial ultramarine, which eventually almost completely replaced the natural product. In 1878 German chemists synthesized

. This product rapidly replaced natural indigo, wiping out vast farms growing indigo. It is now the blue of blue jeans. As the pace of

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, ...

accelerated, a succession of synthetic blue dyes were discovered including

Indanthrone blue Indanthrone blue, also called indanthrene, is an organic compound with the formula . It is a dark blue solid that is a common dye as well as a precursor to other dyes. Preparation The compound made from 2- aminoanthraquinone treated with potass ...

, which had even greater resistance to fading during washing or in the sun, and

copper phthalocyanine Copper phthalocyanine (CuPc), also called phthalocyanine blue, phthalo blue and many other names, is a bright, crystalline, synthetic blue pigment from the group of phthalocyanine dyes. Its brilliant blue is frequently used in paints and dy ...

. File:The Blue Boy.jpg,

The Blue Boy ''The'' () is a grammatical article in English, denoting persons or things already mentioned, under discussion, implied or otherwise presumed familiar to listeners, readers, or speakers. It is the definite article in English. ''The'' is the m ...

(1770), featuring lapis lazuli, indigo, and cobalt colourants, File:Great Wave off Kanagawa2.jpg,

The Great Wave off Kanagawa is a woodblock print by Japanese ''ukiyo-e'' artist Hokusai, created in late 1831 during the Edo period of Japanese history. The print depicts three boats moving through a storm-tossed sea, with a large wave forming a spiral in the centre ...

illustrates the use of

File:Indigoproduktion BASF 1890.JPG, A synthetic indigo dye factory in Germany in 1890.

Dyes for textiles and food

Blue dyes are organic compounds, both synthetic and natural.

Woad ''Isatis tinctoria'', also called woad (), dyer's woad, or glastum, is a flowering plant in the family Brassicaceae (the mustard family) with a documented history of use as a blue dye and medicinal plant. Its genus name, Isatis, derives from ...

and true indigo were once used but since the early 1900s, all indigo is synthetic. Produced on an industrial scale, indigo is the blue of blue jeans. For food, the triarylmethane dye

Brilliant blue FCF Brilliant blue FCF (Blue 1) is a synthetic organic compound used primarily as a blue colorant for processed foods, medications, dietary supplements, and cosmetics. It is classified as a triarylmethane dye and is known under various names, such ...

is used for candies. The search continues for stable, natural blue dyes suitable for the food industry.

Pigments for painting and glass

Blue

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...

s were once produced from minerals, especially lapis lazuli and its close relative

. These minerals were crushed, ground into powder, and then mixed with a quick-drying binding agent, such as egg yolk (

tempera painting Tempera (), also known as egg tempera, is a permanent, fast-drying painting medium consisting of colored pigments mixed with a water-soluble binder medium, usually glutinous material such as egg yolk. Tempera also refers to the paintings done ...

); or with a slow-drying oil, such as linseed oil, for

oil painting Oil painting is the process of painting with pigments with a medium of drying oil as the binder. It has been the most common technique for artistic painting on wood panel or canvas for several centuries, spreading from Europe to the rest of ...

. Two inorganic but synthetic blue pigments are cerulean blue (primarily cobalt(II) stanate: ) and

(milori blue: primarily ). The chromophore in blue

glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...

and glazes is

cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, p ...

(II). Diverse cobalt(II) salts such as cobalt carbonate or cobalt(II) aluminate are mixed with the silica prior to firing. The cobalt occupies sites otherwise filled with silicon.

Inks

Methyl blue Methyl blue is a chemical compound with the molecular formula C37H27N3Na2O9S3. It is used as a stain in histology, and stains collagen blue in tissue sections. It can be used in some differential staining techniques such as Mallory's connect ...

is the dominant blue pigment in inks used in pens.

Blueprint A blueprint is a reproduction of a technical drawing or engineering drawing using a contact print process on light-sensitive sheets. Introduced by Sir John Herschel in 1842, the process allowed rapid and accurate production of an unlimited number ...

ing involves the production of

in situ.

Inorganic compounds

Certain metal

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

s characteristically form blue solutions or blue salts. Of some practical importance,

is used to make the deep blue glazes and glasses. It substitutes for

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

ions in these materials. Cobalt is the blue chromophore in stained glass windows, such as those in

Gothic cathedrals Gothic cathedrals and churches are religious buildings created in Europe between the mid-12th century and the beginning of the 16th century. The cathedrals are notable particularly for their great height and their extensive use of stained glass ...

and in Chinese

porcelain Porcelain () is a ceramic material made by heating substances, generally including materials such as kaolinite, in a kiln to temperatures between . The strength and translucence of porcelain, relative to other types of pottery, arises main ...

beginning in the

T'ang Dynasty The Tang dynasty (, ; zh, t= ), or Tang Empire, was an imperial dynasty of China that ruled from 618 to 907 AD, with an interregnum between 690 and 705. It was preceded by the Sui dynasty and followed by the Five Dynasties and Ten Kingd ...

Copper(II) Copper is a chemical element with the Symbol (chemistry), symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductility, ductile metal with very high thermal conductivity, thermal and electrical conductivity. A fre ...

(Cu²⁺) also produces many blue compounds, including the commercial

algicide Algaecide or algicide is a biocide used for killing and preventing the growth of algae, often defined in a loose sense that, beyond the biological definition, also includes cyanobacteria ("blue-green algae"). An algaecide may be used for controlled ...

copper(II) sulfate Copper(II) sulfate, also known as copper sulphate, is an inorganic compound with the chemical formula . It forms hydrates , where ''n'' can range from 1 to 7. The pentahydrate (''n'' = 5), a bright blue crystal, is the most commonly encountered h ...

(CuSO₄^.5H₂O). Similarly,

vanadyl The vanadyl or oxovanadium(IV) cation, VO2+, is a functional group that is common in the coordination chemistry of vanadium. Complexes containing this functional group are characteristically blue and paramagnetic. A triple bond is proposed to ex ...

salts and solutions are often blue, e.g. vanadyl sulfate.

In nature

Sky and sea

When sunlight passes through the atmosphere, the blue wavelengths are scattered more widely by the oxygen and nitrogen molecules, and more blue comes to our eyes. This effect is called

, after

Lord Rayleigh John William Strutt, 3rd Baron Rayleigh, (; 12 November 1842 – 30 June 1919) was an English mathematician and physicist who made extensive contributions to science. He spent all of his academic career at the University of Cambridge. Am ...

and confirmed by

Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...

in 1911. The sea is seen as blue for largely the same reason: the water absorbs the longer wavelengths of red and reflects and scatters the blue, which comes to the eye of the viewer. The deeper the observer goes, the darker the blue becomes. In the open sea, only about one per cent of light penetrates to a depth of 200 metres. (See underwater and euphotic depth) The colour of the sea is also affected by the colour of the sky, reflected by particles in the water; and by algae and plant life in the water, which can make it look green; or by sediment, which can make it look brown. The farther away an object is, the more blue it often appears to the eye. For example, mountains in the distance often appear blue. This is the effect of

atmospheric perspective Aerial perspective, or atmospheric perspective, refers to the effect the atmosphere has on the appearance of an object as viewed from a distance. As the distance between an object and a viewer increases, the contrast between the object and its ...

; the farther an object is away from the viewer, the less contrast there is between the object and its background colour, which is usually blue. In a painting where different parts of the composition are blue, green and red, the blue will appear to be more distant, and the red closer to the viewer. The cooler a colour is, the more distant it seems. Blue light is scattered more than other wavelengths by the gases in the atmosphere, hence our "blue planet". File:Top of Atmosphere.jpg, Earth's blue

halo Halo, halos or haloes usually refer to: * Halo (optical phenomenon) * Halo (religious iconography), a ring of light around the image of a head HALO, halo, halos or haloes may also refer to: Arts and entertainment Video games * ''Halo'' (franch ...

when seen from space. File:Aerial perspective 1.JPG, Another example of

. File:LightningVolt Deep Blue Sea.jpg, The sea.

Minerals

Lapis-lazuli hg.jpg,

Lapis-lazuli Lapis lazuli (; ), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color. As early as the 7th millennium BC, lapis lazuli was mined in the Sar-i Sang mine ...

Azurite from China.jpg,

Azurite Azurite is a soft, deep-blue copper mineral produced by weathering of copper ore deposits. During the early 19th century, it was also known as chessylite, after the type locality at Chessy-les-Mines near Lyon, France. The mineral, a basic carb ...

Natural ultramarine pigment.jpg, Natural ultramarine pigment Logan Sapphire SI.jpg,

Logan sapphire The Logan Sapphire is a sapphire from Sri Lanka. One of the largest blue faceted sapphires in the world, it was owned by Sir Victor Sassoon and then purchased by M. Robert Guggenheim as a gift for his wife, Rebecca Pollard Guggenheim, who dona ...

Some of the most desirable gems are blue, including

sapphire Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sa ...

and

tanzanite Tanzanite is the blue and violet variety of the mineral zoisite (a calcium aluminium hydroxyl sorosilicate), caused by small amounts of vanadium. Tanzanite belongs to the epidote mineral group. Tanzanite is only found in Simanjiro District of Ma ...

. Compounds of copper(II) are characteristically blue and so are many copper-containing minerals.

(, with a deep blue colour, was once employed in medieval years, but it is unstable pigment, losing its colour especially under dry conditions. Lapis lazuli, mined in Afghanistan for more than three thousand years, was used for jewelry and ornaments, and later was crushed and powdered and used as a pigment. The more it was ground, the lighter the blue colour became. Natural

, made was the finest available blue pigment in the Middle Ages and the

. It was extremely expensive, and in

Italian Renaissance The Italian Renaissance ( it, Rinascimento ) was a period in Italian history covering the 15th and 16th centuries. The period is known for the initial development of the broader Renaissance culture that spread across Europe and marked the trans ...

art, it was often reserved for the robes of the

Virgin Mary Mary; arc, ܡܪܝܡ, translit=Mariam; ar, مريم, translit=Maryam; grc, Μαρία, translit=María; la, Maria; cop, Ⲙⲁⲣⲓⲁ, translit=Maria was a first-century Jewish woman of Nazareth, the wife of Joseph and the mother of ...

Plants and fungi

File:Blaue Primeln.JPG, ''Primula acaulis'' File:Ipomoea August 2007-1.jpg, Morning glory ('' Ipomoea acuminata'') File:Vaccinium corymbosum Beeren.jpg, ''

Vaccinium corymbosum ''Vaccinium corymbosum'', the northern highbush blueberry, is a North American species of blueberry which has become a food crop of significant economic importance. It is native to eastern Canada and the eastern and southern United States, from O ...

'' File:Delphinium denudatum 1.jpg, Blue Delphinium flower File:Lactarius indigo 48568 edit.jpg, ''

Lactarius indigo ''Lactarius indigo'', commonly known as the indigo milk cap, indigo milky, the indigo (or blue) lactarius, or the blue milk mushroom, is a species of agaric fungus in the family Russulaceae. A widely distributed species, it grows naturally i ...

'' Intense efforts have focused on blue flowers and the possibility that natural blue colourants could be used as food dyes. Commonly, blue colours in plants are anthocyanins: "the largest group of water-soluble pigments found widespread in the plant kingdom." In the few plants that exploit structural colouration, brilliant colours are produced by structures within cells. The most brilliant blue colouration known in any living tissue is found in the marble berries of ''

Pollia condensata ''Pollia condensata'', sometimes called the marble berry, is a perennial herbaceous plant with stoloniferous stems and hard, dry, shiny, round, metallic blue fruit. It is found in forested regions of Africa. The blue colour of the fruit, created ...

'', where a spiral structure of cellulose fibrils scattering blue light. The fruit of

quandong Quandong, quandang or quondong, is a common name for the species '' Santalum acuminatum'' (desert, sweet, Western quandong), especially its edible fruit, but may also refer to * '' Aceratium concinnum'' (highroot quandong) * '' Peripentadenia mea ...

(Santalum acuminatum) can appear blue owing to the same effect.

Animals

File:Morpho didius Male Dos MHNT.jpg, Morpho butterfly File:Indigo Bunting by Dan Pancamo 4.jpg,

Indigo bunting The indigo bunting (''Passerina cyanea'') is a small seed-eating bird in the cardinal family, Cardinalidae. It is migratory, ranging from southern Canada to northern Florida during the breeding season, and from southern Florida to northern Sout ...

s have iridescent feathers. File:Mandrill-k-means.png, Blue facial ridges of mandrill File:2009-03-29Dendrobates tinctorius azureus106.jpg,

Blue poison dart frog The blue poison dart frog or blue poison arrow frog (''Dendrobates tinctorius "azureus"'') is a poison dart frog found in the forests surrounded by the Sipaliwini Savanna, which is located in southern Suriname (known in Surinamese Dutch and adja ...

File:Synchiropus splendidus 2 Luc Viatour cropped.png, The mandarin fish is one of few animal species with blue pigment File:RanaArvalisBlueMale3.jpg, Male moor frogs become blue during the height of mating season Blue-pigmented animals are relatively rare. Examples of which include butterflies of the genus ''

Nessaea ''Nessaea'' is a genus of nymphalid butterflies found in the Neotropical realm. Unlike virtually all other butterflies with blue coloration, the blue colors in this genus are due to pigmentation terobilin (biliverdin IXγ)ref>Doug Taron"It's al ...

'', where blue is created by pterobilin. Other blue pigments of animal origin include phorcabilin, used by other butterflies in '' Graphium'' and ''

Papilio ''Papilio'' is a genus in the swallowtail butterfly family, Papilionidae, as well as the only representative of the tribe Papilionini. The word ''papilio'' is Latin for butterfly. It includes the common yellow swallowtail (''Papilio machaon''), ...

'' (specifically '' P. phorcas'' and '' P. weiskei''), and sarpedobilin, which is used by ''

Graphium sarpedon ''Graphium sarpedon'', the common bluebottle or blue triangle in Australia, is a species of swallowtail butterfly that is found in South and Southeast Asia, as well as eastern Australia. There are approximately sixteen subspecies with diffe ...

''. Blue-pigmented

organelles In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' th ...

, known as "cyanosomes", exist in the

chromatophore Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast, ...

s of at least two fish species, the mandarin fish and the

picturesque dragonet The picturesque dragonet (''Synchiropus picturatus'') is a brightly colored member of the dragonet family native to the Indo-West Pacific: Philippines, eastern Indonesia and northwest Australia. It occasionally makes its way into the aquarium tr ...

. More commonly, blueness in animals is a

; an optical interference effect induced by organized nanometer-sized scales or fibres. Examples include the plumage of several birds like the blue jay and

indigo bunting The indigo bunting (''Passerina cyanea'') is a small seed-eating bird in the cardinal family, Cardinalidae. It is migratory, ranging from southern Canada to northern Florida during the breeding season, and from southern Florida to northern Sout ...

, the scales of butterflies like the morpho butterfly, collagen fibres in the skin of some species of monkey and opossum, and the iridophore cells in some fish and frogs.

Eyes

Blue eyes do not actually contain any blue pigment.

Eye colour Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

is determined by two factors: the

ation of the eye's

iris Iris most often refers to: *Iris (anatomy), part of the eye *Iris (mythology), a Greek goddess * ''Iris'' (plant), a genus of flowering plants * Iris (color), an ambiguous color term Iris or IRIS may also refer to: Arts and media Fictional ent ...

and the scattering of light by the

turbid Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids can ...

medium in the stroma of the iris. In humans, the pigmentation of the iris varies from light brown to black. The appearance of blue, green, and hazel eyes results from the

Tyndall scattering The Tyndall effect is light scattering by particles in a colloid or in a very fine suspension. Also known as Tyndall scattering, it is similar to Rayleigh scattering, in that the intensity of the scattered light is inversely proportional to the ...

of light in the stroma, an optical effect similar to what accounts for the blueness of the sky. The irises of the eyes of people with blue eyes contain less dark

melanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...

than those of people with brown eyes, which means that they absorb less short-wavelength blue light, which is instead reflected out to the viewer. Eye colour also varies depending on the lighting conditions, especially for lighter-coloured eyes. Blue eyes are most common in Ireland, the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and ...

area and Northern Europe, and are also found in

Eastern Eastern may refer to: Transportation *China Eastern Airlines, a current Chinese airline based in Shanghai *Eastern Air, former name of Zambia Skyways *Eastern Air Lines, a defunct American airline that operated from 1926 to 1991 *Eastern Air Li ...

, Central, and

Southern Europe Southern Europe is the southern region of Europe. It is also known as Mediterranean Europe, as its geography is essentially marked by the Mediterranean Sea. Definitions of Southern Europe include some or all of these countries and regions: Alba ...

. Blue eyes are also found in parts of Western Asia, most notably in Afghanistan, Syria, Iraq, and Iran. In

Estonia Estonia, formally the Republic of Estonia, is a country by the Baltic Sea in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the sea across from Sweden, to the south by Latvia, a ...

, 99% of people have blue eyes. In Denmark in 1978, only 8% of the population had brown eyes, though through immigration, today that number is about 11%. In Germany, about 75% have blue eyes. In the United States, as of 2006, one out of every six people, or 16.6% of the total population, and 22.3% of the white population, have blue eyes, compared with about half of Americans born in 1900, and a third of Americans born in 1950. Blue eyes are becoming less common among American children. In the US, boys are 3–5 per cent more likely to have blue eyes than girls.

History

In the ancient world

File:Lapis bowl Iran.JPG, Lapis lazuli bowl from Iran, end of 3rd – beginning of 2nd millennium BC (Louvre Museum) File:Tripodic goblet Louvre AO4079.jpg,

tripodic beaker imitating lapis lazuli. South Mesopotamia. (1399-1200 BC) File:WLA metmuseum Wall painting Polyphemus and Galaltea 4.jpg, Fresco of Polyphemus and Galatea, Pompei, using

(1st c. BC) (Metropolitan Museum) As early as the

7th millennium BC The 7th millennium BC spanned the years 7000 BC to 6001 BC (c. 9 ka to c. 8 ka). It is impossible to precisely date events around this millennium, and all dates mentioned here are estimates mostly based on geological and anthropological analysi ...

, lapis lazuli was mined in the

Sar-i Sang Sar-i Sang (or Sar-e Sang) (lit. "stone summit" in Persian) is a settlement in the Kuran Wa Munjan District of Badakhshan Province, Afghanistan, famous for its ancient lapis lazuli mines producing the world's finest lapis. It is located in the ...

mines,David Bomford and Ashok Roy, ''A Closer Look- Colour'' (2009), National Gallery Company, London, () in

Shortugai Shortugai (Shortughai), in Darqad District of northern Afghanistan, was a trading colony of the Indus Valley civilization (or Harappan Civilization) established around 2000 BC on the Oxus river (Amu Darya) near the lapis lazuli mines. It is co ...

, and in other mines in

Badakhshan Badakhshan is a historical region comprising parts of modern-day north-eastern Afghanistan, eastern Tajikistan, and Taxkorgan Tajik Autonomous County in China. Badakhshan Province is one of the 34 provinces of Afghanistan. Much of historic Ba ...

province in northeast

Afghanistan Afghanistan, officially the Islamic Emirate of Afghanistan,; prs, امارت اسلامی افغانستان is a landlocked country located at the crossroads of Central Asia and South Asia. Referred to as the Heart of Asia, it is bordere ...

. Lapis lazuli artifacts, dated to 7570 BC, have been found at

Bhirrana Bhirrana, also Bhirdana and Birhana, (Hindi: भिरड़ाना; IAST: Bhirḍāna) is an archaeological site, located in a small village in Fatehabad District, in the Indian state of Haryana. Bhirrana's earliest archaeological layers pr ...

, which is the oldest site of

Indus Valley civilisation The Indus Valley Civilisation (IVC), also known as the Indus Civilisation was a Bronze Age civilisation in the northwestern regions of South Asia, lasting from 3300 BCE to 1300 BCE, and in its mature form 2600 BCE to 1900& ...

. Lapis was highly valued by the Indus Valley Civilisation (7570–1900 BC). Lapis beads have been found at

Neolithic The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several p ...

burials in

Mehrgarh Mehrgarh (; ur, ) is a Neolithic archaeological site (dated ) situated on the Kacchi Plain of Balochistan in Pakistan. It is located near the Bolan Pass, to the west of the Indus River and between the modern-day Pakistani cities of Quetta, ...

, the

Caucasus The Caucasus () or Caucasia (), is a region between the Black Sea and the Caspian Sea, mainly comprising Armenia, Azerbaijan, Georgia (country), Georgia, and parts of Southern Russia. The Caucasus Mountains, including the Greater Caucasus range ...

, and as far away as Mauritania. It was used in the funeral mask of Tutankhamun (1341–1323 BC). A term for Blue was relatively rare in many forms of ancient art and decoration, and even in ancient literature. The Ancient Greek poets described the sea as green, brown or "the colour of wine". The colour was not mentioned in the

Hebrew Bible The Hebrew Bible or Tanakh (;"Tanach"
'' cave paintings from the Upper Paleolithic period, but not blue. Blue was also not used for dyeing fabric until long after red, ochre, pink, and purple. This is probably due to the perennial difficulty of making blue dyes and pigments. On the other hand, the rarity of blue pigment made it even more valuable. The earliest known blue dyes were made from plants –

in Europe,

in Asia and Africa, while blue pigments were made from minerals, usually either lapis lazuli or

azurite Azurite is a soft, deep-blue copper mineral produced by weathering of copper ore deposits. During the early 19th century, it was also known as chessylite, after the type locality at Chessy-les-Mines near Lyon, France. The mineral, a basic carb ...

, and required more. Blue glazes posed still another challenge since the early blue dyes and pigments were not thermally robust. In ca. 2500 BC, the blue glaze

was introduced for ceramics, as well as many other objects.Chase, W.T. 1971, "Egyptian blue as a pigment and ceramic material." In: R. Brill (ed.) ''Science and Archaeology''. Cambridge, Mass: MIT Press. The Greeks imported indigo dye from India, calling it indikon, and they painted with Egyptian blue. Blue was not one of the four primary colours for Greek painting described by

Pliny the Elder Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic ' ...

(red, yellow, black, and white). For the Romans, blue was the colour of mourning, as well as the colour of barbarians. The Celts and Germans reportedly dyed their faces blue to frighten their enemies, and tinted their hair blue when they grew old. The Romans made extensive use of indigo and Egyptian blue pigment, as evidenced, in part, by frescos in Pompeii. The Romans had many words for varieties of blue, including , , , , , , , and , but two words, both of foreign origin, became the most enduring; , from the Germanic word ''blau'', which eventually became ''bleu'' or blue; and , from the Arabic word , which became azure. Blue was widely used in the decoration of churches in the Byzantine Empire. By contrast, in the Islamic world, blue was of secondary to green, believed to be the favourite colour of the

Prophet Mohammed Muhammad ( ar, مُحَمَّد; 570 – 8 June 632 CE) was an Arab religious, social, and political leader and the founder of Islam. According to Islamic doctrine, he was a prophet divinely inspired to preach and confirm the monoth ...

. At certain times in

Moorish Spain Al-Andalus DIN 31635, translit. ; an, al-Andalus; ast, al-Ándalus; eu, al-Andalus; ber, ⴰⵏⴷⴰⵍⵓⵙ, label=Berber languages, Berber, translit=Andalus; ca, al-Àndalus; gl, al-Andalus; oc, Al Andalús; pt, al-Ândalus; es, ...

and other parts of the Islamic world, blue was the colour worn by Christians and Jews, because only Muslims were allowed to wear white and green.

In the Middle Ages

File:Vitraux Saint-Denis 190110 19.jpg, Stained glass window at

Saint Denis Basilica The Basilica of Saint-Denis (french: Basilique royale de Saint-Denis, links=no, now formally known as the ) is a large former medieval abbey church and present cathedral in the commune of Saint-Denis, a northern suburb of Paris. The building ...

(1130-1140), coloured with cobalt blue File:Vitrail Chartres Notre-Dame 210209 1.jpg, Detail of the Blue Virgin Window,

Chartres Cathedral Chartres Cathedral, also known as the Cathedral of Our Lady of Chartres (french: Cathédrale Notre-Dame de Chartres), is a Roman Catholic church in Chartres, France, about southwest of Paris, and is the seat of the Bishop of Chartres. Mostly con ...

(12th c.) File:Wilton diptych.jpg, The

Wilton Diptych The Wilton Diptych () is a small portable diptych of two hinged panels, painted on both sides, now in the National Gallery, London. It is an extremely rare survival of a late medieval religious panel painting from England. The diptych was pain ...

(1395–1399). The

was traditionally shown in blue(14th c.) In the art and life of Europe during the early

, blue played a minor role. This changed dramatically between 1130 and 1140 in Paris, when the

Abbe Suger Suger (; la, Sugerius; 1081 – 13 January 1151) was a French abbot, statesman, and historian. He once lived at the court of Pope Calixtus II in Maguelonne, France. He later became abbot of St-Denis, and became a close confidant to King Lou ...

rebuilt the

. Suger considered that light was the visible manifestation of the Holy Spirit. He installed stained glass windows coloured with

, which, combined with the light from the red glass, filled the church with a bluish violet light. The church became the marvel of the

Christian world Christendom historically refers to the Christian states, Christian-majority countries and the countries in which Christianity dominates, prevails,SeMerriam-Webster.com : dictionary, "Christendom"/ref> or is culturally or historically intertwin ...

, and the colour became known as the . In the years that followed even more elegant blue stained glass windows were installed in other churches, including at

and

Sainte-Chapelle The Sainte-Chapelle (; en, Holy Chapel) is a royal chapel in the Gothic style, within the medieval Palais de la Cité, the residence of the Kings of France until the 14th century, on the Île de la Cité in the River Seine in Paris, France. ...

in Paris. In the 12th century the Roman Catholic Church dictated that painters in Italy (and the rest of Europe consequently) to paint the Virgin Mary with blue, which became associated with holiness, humility and virtue. In medieval paintings, blue was used to attract the attention of the viewer to the Virgin Mary. Paintings of the mythical King Arthur began to show him dressed in blue. The coat of arms of the kings of France became an azure or light blue shield, sprinkled with golden fleur-de-lis or lilies. Blue had come from obscurity to become the royal colour.

Renaissance through 18th century

Blue came into wider use beginning in the Renaissance, when artists began to paint the world with perspective, depth, shadows, and light from a single source. In Renaissance paintings, artists tried to create harmonies between blue and red, lightening the blue with lead white paint and adding shadows and highlights. Raphael was a master of this technique, carefully balancing the reds and the blues so no one colour dominated the picture. Ultramarine was the most prestigious blue of the Renaissance, being more expensive than gold. Wealthy art patrons commissioned works with the most expensive blues possible. In 1616 Richard Sackville, 3rd Earl of Dorset, Richard Sackville commissioned a portrait of himself by Isaac Oliver with three different blues, including ultramarine pigment for his stockings. File:Oliver Richard Sackville Earl of Dorset 1616.jpg, Portrait of Richard Sackville (1616), using three expensive blues, including ultramarine for his stockings File:MET DP251168.jpg, Ming Dynasty, Porcelain vase painted with cobalt blue under transparent glaze. (15th c.) (Metropolitan Museum) File:Delftware plaque with New Testament scene 002.jpg, Delftware plaque with cobalt blue painting (1683) (Rijksmuseum, Amsterdam) File:Urn with cover MET DP104608.jpg, Urn by Josiah Wedgewood (1780s) (Metropolitan Museum) File:Johannes Vermeer - Girl with a Pearl Earring - WGA24666.jpg, "Girl with a Pearl Earring" by Johannes Vermeer features

pigment An industry for the manufacture of fine blue and white pottery began in the 14th century in Jingdezhen, China, using white Chinese porcelain decorated with patterns of cobalt blue, imported from Persia. It was first made for the family of the Emperor of China, then was exported around the world, with designs for export adapted to European subjects and tastes. The Chinese blue style was also adapted by Dutch craftsmen in Delftware, [Delft and English craftsmen in Staffordshire in the 17th-18th centuries. in the 18th century, blue and white porcelains were produced by Josiah Wedgwood and other British craftsmen.

19th-20th century

File:BrummellDighton1805.jpg, Beau Brummel (1776-1840) introduced the ancestor of the modern blue suit File:A Miner in His Cabin.jpg, A California gold miner in blue jeans (1853) File:Ferdinand Krumholz Isabel do Brasil 1853.jpg, Isabel, Princess Imperial of Brazil in blue gown (1853) File:New York Metropolitan Police Uniforms 1871.jpg, New York City police in 1871 The early 19th century saw the ancestor of the modern blue business suit, created by Beau Brummel (1776-1840), who set fashion at the London Court. It also saw the invention of blue jeans, a highly popular form of workers's costume, invented in 1853 by Jacob W. Davis who used metal rivets to strengthen blue denim work clothing in the California gold fields. The invention was funded by San Francisco entrepreneur Levi Strauss, and spread around the world. . File:Starry Night Over the Rhone.jpg, Van Gogh's ''Starry Night Over the Rhône'' (1888). Blue used to create a mood or atmosphere. A cobalt blue sky, and cobalt or ultramarine water. File:Old guitarist chicago.jpg, Blue conveys melancholy in Pablo Picasso, Picasso's ''The Old Guitarist'' (1903-1904). File:Matisse Conversation.jpg, "The Conversation" by Henri Matisse (1908-1912) Recognizing the emotional power of blue, many artists made it the central element of paintings in the 19th and 20th centuries. They included Picasso's Blue Period, Pablo Picasso, Pavel Kuznetsov and the Blue Rose (art group), Blue Rose art group, and Wassily Kandinsky, Kandinsky and Der Blaue Reiter (The Blue Rider) school.Wassily Kandinsky, M. T. Sadler (Translator) ''Concerning the Spiritual in Art''. Dover Publ. (Paperback). 80 pp. . Henri Matisse expressed deep emotions with blue:, "A certain blue penetrates your soul." In the second half of the 20th century, painters of the abstract expressionist movement use blues to inspire ideas and emotions. Painter Mark Rothko observed that colour was "only an instrument;" his interest was "in expressing human emotions tragedy, ecstasy, doom, and so on."

In society and culture

Uniforms

File:Very friendly MPS officers in London.jpg, Officers of the London Metropolitan Police File:Royal Navy Sailors on Parade MOD 45155635.jpg, Sailors of the Royal Navy File:2010. Донецк. Карнавал на день города 010.jpg, Ukrainian police officer in Donetsk In the 17th century. The Prince-Elector of Brandenburg, Frederick William I of Prussia, chose

as the new colour of Prussian military uniforms, because it was made with

, a local crop, rather than Indigo, which was produced by the colonies of Brandenburg's rival, England. It was worn by the German army until World War I, with the exception of the soldiers of Bavaria, who wore sky-blue. In 1748, the Royal Navy adopted a dark shade of blue for the uniform of officers.Heller (2010) p.32 It was first known as marine blue, now known as

. The militia organized by George Washington selected blue and Buff (colour), buff, the colours of the British Whig (British political party), Whig Party. Blue continued to be the colour of the field uniform of the US Army until 1902, and is still the colour of the dress uniform. In the 19th century, police in the United Kingdom, including the Metropolitan Police and the City of London Police also adopted a navy blue uniform. Similar traditions were embraced in France and Austria. It was also adopted at about the same time for the uniforms of the officers of the New York City Police Department.

Religion

File:Sri Mariamman Temple Singapore 2 amk.jpg, In Hinduism, Krishna is depicted with blue skin File:Reknown blue domes of the Church dedicated to St. Spirou in Firostefani, Santorini island (Thira), Greece.jpg, Blue domes of the Church dedicated to St. Spirou in Firostefani, Santorini island (Thira), Greece. File:Mezquita Shah, Isfahán, Irán, 2016-09-20, DD 64.jpg, Persian blue in Shah mosque (16th c.) in Isfahan, Iran File:Flag-of-Israel-4-Zachi-Evenor.jpg, The flag of Israel uses a special variety of blue, called tekhelet * Blue in Judaism: In the Torah, the Israelites were commanded to put fringes, ''tzitzit'', on the corners of their garments, and to weave within these fringes a "twisted thread of blue (''tekhelet'')". In ancient days, this blue thread was made from a dye extracted from a Mediterranean snail called the ''hilazon''. Maimonides claimed that this blue was the colour of "the clear noonday sky"; Rashi, the colour of the evening sky. According to several rabbinic sages, blue is the colour of God's Glory. Staring at this colour aids in mediation, bringing us a glimpse of the "pavement of sapphire, like the very sky for purity", which is a likeness of the Throne of God. (The Hebrew language, Hebrew word for glory.) Many items in the ''Mishkan'', the portable sanctuary in the wilderness, such as the ''Menorah (Temple), menorah'', many of the vessels, and the Ark of the Covenant, were covered with blue cloth when transported from place to place. * Blue in Christianity: Blue is particularly associated with the Mary (mother of Jesus), Virgin Mary. This was the result of a decree of Pope Gregory I (540-601) who ordered that all religious paintings should tell a story which was clearly comprehensible to all viewers, and that figures should be easily recognizable, especially that of the figure of Mary. If she was alone in the image, her costume was usually painted with the finest blue,

. If she was with Christ, her costume was usually painted with a less expensive pigment, to avoid outshining him.Heller, "Psychologie de la Colour - Effets et Symboliques", (2009),p. 32 * Blue in Hinduism: Many of the gods are depicted as having blue-coloured skin, particularly those associated with Vishnu, who is said to be the preserver of the world, and thus intimately connected to water. Krishna and Rama, Vishnu's avatars, are usually depicted with blue skin. Shiva, the destroyer deity, is also depicted in a light-blue hue, and is called ''neela kantha'', or blue-throated, for having swallowed poison to save the universe during the Samudra Manthana, the churning of the ocean of milk. Blue is used to symbolically represent the fifth, and the throat, chakra (Vishuddha). * Blue in Sikhism: The Nihang, Akali Nihangs warriors wear all-blue attire. Guru Gobind Singh also has a Roan (horse), blue roan horse. The Sikh Rehat Maryada states that the Nishan Sahib hoisted outside every Gurdwara, Gurudwara should be yellow, xanthic (Basanti in Punjabi language, Punjabi) or greyish blue (modern day

) (Surmaaee in Punjabi language, Punjabi) colour. *Blue in Paganism: Blue is associated with peace, truth, wisdom, protection, and patience. It helps with healing, psychic ability, harmony, and understanding.

Sports

File:Italy Team - Rome, 1965.jpg, The Italy national football team, Italian national football team File:Serbia national volleyball team at the 2012 Summer Olympics (7913882066).jpg, Serbian national volleyball team, 2012 Olympics In sports, blue is widely represented in uniforms in part because the majority of national teams wear the colours of their national flag. For example, the World Cup-winning France national football team, France are known as ''Les Bleus'' (the Blues). Similarly, Argentina national football team, Argentina, Italy national football team, Italy, and Uruguay national football team, Uruguay wear blue shirts. The Asian Football Confederation and the Oceania Football Confederation use blue text on their logos. Blue is well represented in baseball (Toronto Blue Jays, Blue Jays, National Basketball Association, basketball, and National Football League, American football, and National Hockey League, Ice hockey. The India national cricket team, Indian national cricket team wears blue uniform during One day international matches, as such the team is also referred to as "Men in Blue".

Politics

File:Flag of the United Nations.svg, Flag of the

, approximates "sky blue" File:Flag of Europe.svg, Flag of the

is "reflex blue", a medium dark blue File:Red state, blue state.svg, A presidential-election map of the US, 2004–2016. States that consistently vote for Democrats are termed "blue states". Unlike red or green, blue was not strongly associated with any particular country, religion or political movement. As the colour of harmony, it was chosen as the colour for the flags of the

, the

, and NATO.Heller, "Psychologie de la Couleur" pp. 36-37 In politics, blue is sometimes used as the colour of conservative parties, contrasting with the red of more leftist parties. It is the colour of the British Conservative Party (UK), Conservative party. However, in the United States, the colours are reversed. To avoid associations of the Democrats with socialism or the far left, States which voted Democratic in four consecutive presidential elections are termed "blue states", while those which voted for Republicans are termed "red states". States which voted for different parties in two of the last four presidential elections are called "Swing States", and are usually coloured purple, a mix of red and blue, or sometimes pink or light blue.

References

Works cited

* (page numbers refer to the French translation) * * * * * * *

External links

* *
"Friday essay: from the Great Wave to Starry Night, how a blue pigment changed the world", By Dr Hugh Davies, theconversation.com
{{Authority control Primary colors Secondary colors Optical spectrum Rainbow colors Shades of blue, Web colors

Etymology and linguistics

Optics and colour theory

Shades and variations

As a structural colour

Colourants

Artificial blues

Dyes for textiles and food

Pigments for painting and glass

Inks

Inorganic compounds

In nature

Sky and sea

Minerals

Plants and fungi

Animals

Eyes

History

In the ancient world

In the Middle Ages

Renaissance through 18th century

19th-20th century

In society and culture

Uniforms

Religion

Sports

Politics

See also

References

Works cited

Further reading

External links