Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet 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 ...

of visible light. 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 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 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 ultramarine, 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 cathedrals. Europeans wore clothing coloured with the vegetable dye woad until it was replaced by the finer indigo 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. 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.) 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 (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 included blue as one of the seven colours in his first description the visible spectrum. 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 indigo, 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, blue is one of the three primary colours of pigments (red, yellow, blue), which can be mixed to form a wide gamut 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 ...

by Jacob Christoph Le Blon 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 colours 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; that is, a colour corresponding to an equal mixture of

and green 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). Lasers 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 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 violet and cyan on the visible spectrum. Hues of blue include indigo and ultramarine, 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 green, and the other blue-greens such as turquoise, teal, 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).

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, 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. 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. 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. 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, 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 ultramarine 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 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 indigo. 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, which had even greater resistance to fading during washing or in the sun, and copper phthalocyanine. File:The Blue Boy.jpg, The Blue Boy (1770), featuring lapis lazuli, indigo, and cobalt colourants, File:Great Wave off Kanagawa2.jpg, The Great Wave off Kanagawa 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 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 pigments were once produced from minerals, especially lapis lazuli and its close relative ultramarine. These minerals were crushed, ground into powder, and then mixed with a quick-drying binding agent, such as egg yolk ( tempera painting); 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(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 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 ions characteristically form blue solutions or blue salts. Of some practical importance, cobalt is used to make the deep blue glazes and glasses. It substitutes for silicon or aluminum ions in these materials. Cobalt is the blue chromophore in stained glass windows, such as those in Gothic cathedrals 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. Copper(II) (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 (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; 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 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 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. Azurite (, 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 ultramarine, 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.

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'' 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'', where a spiral structure of cellulose fibrils scattering blue light. The fruit of quandong (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 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'' (specifically '' P. phorcas'' and '' P. weiskei''), and sarpedobilin, which is used by '' Graphium sarpedon''. Blue-pigmented organelles, 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 is determined by two factors: the pigmentation 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 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 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 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. 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 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 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, which is the oldest site of Indus Valley civilisation. Lapis was highly valued by the Indus Valley Civilisation (7570–1900 BC). Lapis beads have been found at Neolithic burials in Mehrgarh, 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 – woad in Europe, indigo in Asia and Africa, while blue pigments were made from minerals, usually either lapis lazuli or azurite, 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. At certain times in Moorish Spain 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 Virgin Mary 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 cobalt, 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 The fleur-de-lis, also spelled fleur-de-lys (plural ''fleurs-de-lis'' or ''fleurs-de-lys''), is a lily (in French, and mean 'flower' and 'lily' respectively) that is used as a decorative design or symbol. The fleur-de-lis has been used in the ...

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 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 Delftware or Delft pottery, also known as Delft Blue ( nl, Delfts blauw) or as delf, is a general term now used for Dutch tin-glazed earthenware, a form of faience. Most of it is blue and white pottery, and the city of Delft in the Netherlands ...

plaque with cobalt blue painting (1683) (Rijksmuseum, Amsterdam) File:Urn with cover MET DP104608.jpg, Urn by

Josiah Wedgewood Josiah Wedgwood (12 July 1730 – 3 January 1795) was an English potter, entrepreneur and abolitionist. Founding the Wedgwood company in 1759, he developed improved pottery bodies by systematic experimentation, and was the leader in the indu ...

(1780s) (Metropolitan Museum) File:Johannes Vermeer - Girl with a Pearl Earring - WGA24666.jpg, "Girl with a Pearl Earring" by

Johannes Vermeer Johannes Vermeer ( , , see below; also known as Jan Vermeer; October 1632 – 15 December 1675) was a Dutch Baroque Period painter who specialized in domestic interior scenes of middle-class life. During his lifetime, he was a moderately succe ...

features ultramarine pigment An industry for the manufacture of fine blue and white pottery began in the 14th century in

Jingdezhen Jingdezhen is a prefecture-level city, in northeastern Jiangxi province, with a total population of 1,669,057 (2018), bordering Anhui to the north. It is known as the " Porcelain Capital" because it has been producing Chinese ceramics for at le ...

, 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 elft 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 Denim is a sturdy cotton warp-faced textile in which the weft passes under two or more warp threads. This twill weaving produces a diagonal ribbing that distinguishes it from cotton duck. While a denim predecessor known as dungaree has been p ...

work clothing in the California gold fields. The invention was funded by San Francisco entrepreneur

Levi Strauss Levi Strauss (; born Löb Strauß ; February 26, 1829 – September 26, 1902) was a German-born American businessman who founded the first company to manufacture blue jeans. His firm of Levi Strauss & Co. (Levi's) began in 1853 in San Francisc ...

, and spread around the world. . File:Starry Night Over the Rhone.jpg, Van Gogh's ''

Starry Night Over the Rhône ''Starry Night'' (September 1888, french: La Nuit étoilée), commonly known as ''Starry Night Over the Rhône'', is one of Vincent van Gogh's paintings of Arles at night. It was painted on the bank of the Rhône that was only a one or two-min ...

'' (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 Picasso's ''

The Old Guitarist ''The Old Guitarist'' is an oil painting by Pablo Picasso, which he created in late 1903 and early 1904. It depicts an elderly musician, a haggard man with threadbare clothing, who is hunched over his guitar while playing in the streets of Barc ...

'' (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 Pablo Picasso,

Pavel Kuznetsov Pavel Varfolomevich Kuznetsov (1878–1968) was a Russian painter and graphic artist. Life and career He studied at Saratov at Bogolyubov Art School (1891–1896), then Moscow School of Painting, Sculpture and Architecture (1897–1904) and f ...

and the

Blue Rose A blue rose is a flower of the genus ''Rosa'' (family Rosaceae) that presents blue-to-violet pigmentation instead of the more common red, white, or yellow. Blue roses are often used to symbolize mystery or attaining the impossible. However, beca ...

art group, and

Kandinsky Wassily Wassilyevich Kandinsky (; rus, Василий Васильевич Кандинский, Vasiliy Vasilyevich Kandinskiy, vɐˈsʲilʲɪj vɐˈsʲilʲjɪvʲɪtɕ kɐnʲˈdʲinskʲɪj; – 13 December 1944) was a Russian painter a ...

and

Der Blaue Reiter ''Der Blaue Reiter'' (The Blue Rider) is a designation by Wassily Kandinsky and Franz Marc for their exhibition and publication activities, in which both artists acted as sole editors in the almanac of the same name, first published in mid-May ...

(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 Mark Rothko (), born Markus Yakovlevich Rothkowitz (russian: Ма́ркус Я́ковлевич Ротко́вич, link=no, lv, Markuss Rotkovičs, link=no; name not Anglicized until 1940; September 25, 1903 – February 25, 1970), was a Lat ...

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 The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against ...

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 Woad, 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

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 George Washington (February 22, 1732, 1799) was an American military officer, statesman, and Founding Father who served as the first president of the United States from 1789 to 1797. Appointed by the Continental Congress as commander of ...

selected blue and buff, the colours of the British 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 The New York City Police Department (NYPD), officially the City of New York Police Department, established on May 23, 1845, is the primary municipal law enforcement agency within the City of New York, the largest and one of the oldest in ...

Religion

File:Sri Mariamman Temple Singapore 2 amk.jpg, In

Hinduism Hinduism () is an Indian religion or '' dharma'', a religious and universal order or way of life by which followers abide. As a religion, it is the world's third-largest, with over 1.2–1.35 billion followers, or 15–16% of the global p ...

, 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 ''Tekhelet'' ( he, תְּכֵלֶת ''təḵēleṯ''; alternate spellings include ''tekheleth'', ''t'chelet'', ''techelet'' and ''techeiles'') is a "blue-violet", "blue", or "turquoise" dye highly prized by ancient Mediterranean civilizations. I ...

: 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 Musa ibn Maimon (1138–1204), commonly known as Maimonides (); la, Moses Maimonides and also referred to by the acronym Rambam ( he, רמב״ם), was a Sephardic Jewish philosopher who became one of the most prolific and influential Tora ...

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 Hebrew (; ; ) is a Northwest Semitic language of the Afroasiatic language family. Historically, it is one of the spoken languages of the Israelites and their longest-surviving descendants, the Jews and Samaritans. It was largely preserved ...

word for glory.) Many items in the ''

Mishkan According to the Hebrew Bible, the tabernacle ( he, מִשְׁכַּן, mīškān, residence, dwelling place), also known as the Tent of the Congregation ( he, link=no, אֹהֶל מוֹעֵד, ’ōhel mō‘ēḏ, also Tent of Meeting, etc.), ...

'', the portable sanctuary in the wilderness, such as the '' 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 Christianity is an Abrahamic monotheistic religion based on the life and teachings of Jesus of Nazareth. It is the world's largest and most widespread religion with roughly 2.38 billion followers representing one-third of the global pop ...

: Blue is particularly associated with the 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, ultramarine. 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

: Many of the gods are depicted as having blue-coloured skin, particularly those associated with

Vishnu Vishnu ( ; , ), also known as Narayana and Hari, is one of the principal deities of Hinduism. He is the supreme being within Vaishnavism, one of the major traditions within contemporary Hinduism. Vishnu is known as "The Preserver" withi ...

, who is said to be the preserver of the world, and thus intimately connected to water. Krishna and

Rama Rama (; ), Ram, Raman or Ramar, also known as Ramachandra (; , ), is a major deity in Hinduism. He is the seventh and one of the most popular '' avatars'' of Vishnu. In Rama-centric traditions of Hinduism, he is considered the Supreme Bein ...

, Vishnu's avatars, are usually depicted with blue skin.

Shiva Shiva (; sa, शिव, lit=The Auspicious One, Śiva ), also known as Mahadeva (; ɐɦaːd̪eːʋɐ, or Hara, is one of the principal deities of Hinduism. He is the Supreme Being in Shaivism, one of the major traditions within Hindu ...

, 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 Samudra Manthana ( sa, समुद्रमन्थन; ) is a major episode in Hinduism that is elaborated in the Vishnu Purana, a major text of Hinduism. The Samudra Manthana explains the origin of the elixir of eternal life, amrita. Nom ...

, the churning of the ocean of milk. Blue is used to symbolically represent the fifth, and the throat, chakra ( Vishuddha). * Blue in

Sikhism Sikhism (), also known as Sikhi ( pa, ਸਿੱਖੀ ', , from pa, ਸਿੱਖ, lit=disciple', 'seeker', or 'learner, translit=Sikh, label=none),''Sikhism'' (commonly known as ''Sikhī'') originated from the word ''Sikh'', which comes fro ...

: The Akali Nihangs warriors wear all-blue attire. Guru Gobind Singh also has a blue roan

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...

. The Sikh Rehat Maryada states that the Nishan Sahib hoisted outside every

Gurudwara A gurdwara (sometimes written as gurudwara) (Gurmukhi: ਗੁਰਦੁਆਰਾ ''guradu'ārā'', meaning "Door to the Guru") is a place of assembly and worship for Sikhs. Sikhs also refer to gurdwaras as ''Gurdwara Sahib''. People from all faiths ...

should be xanthic (Basanti in Punjabi) or greyish blue (modern day

) (Surmaaee in 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

Italian national football team The Italy national football team ( it, Nazionale di calcio dell'Italia) has represented Italy in international football since its first match in 1910. The national team is controlled by the Italian Football Federation (FIGC), the governing body ...

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 France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...

are known as ''Les Bleus'' (the Blues). Similarly,

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...

, and

Uruguay Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...

wear blue shirts. The Asian Football Confederation and the Oceania Football Confederation use blue text on their logos. Blue is well represented in

baseball Baseball is a bat-and-ball sport played between two teams of nine players each, taking turns batting and fielding. The game occurs over the course of several plays, with each play generally beginning when a player on the fielding t ...

( Blue Jays,

basketball Basketball is a team sport in which two teams, most commonly of five players each, opposing one another on a rectangular court, compete with the primary objective of shooting a basketball (approximately in diameter) through the defender's h ...

, and

American football American football (referred to simply as football in the United States and Canada), also known as gridiron, is a team sport played by two teams of eleven players on a rectangular field with goalposts at each end. The offense, the team wi ...

, and

Ice hockey Ice hockey (or simply hockey) is a team sport played on ice skates, usually on an ice skating rink with lines and markings specific to the sport. It belongs to a family of sports called hockey. In ice hockey, two opposing teams use ice h ...

. The 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 The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two No ...

.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. 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 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