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Indigo is a deep color close to the color wheel blue (a primary color in the
RGB color space An RGB color space is any additive color space based on the RGB color model. An RGB color space is defined by chromaticity coordinates of the red, green, and blue additive primaries, the white point which is usually a standard illuminant, and t ...
), as well as to some variants of
ultramarine Ultramarine is a deep blue color pigment which was originally made by grinding lapis lazuli into a powder.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 Afgh ...
, based on the ancient dye of the same name. The word "indigo" comes from the Latin word ''indicum'', meaning "Indian", as the dye was originally exported to Europe from
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
. It is traditionally regarded as a color in the
visible spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' or simply light. A typical human eye wil ...
, as well as one of the seven colors of the
rainbow A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows c ...
: the color between
blue 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 of visible light. The eye perceives blue when obs ...
and
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 ...
; however, sources differ as to its actual position in the
electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from ...
. The first known recorded use of indigo as a color name in
English English usually refers to: * English language * English people English may also refer to: Peoples, culture, and language * ''English'', an adjective for something of, from, or related to England ** English national ide ...
was in 1289.


History

''
Indigofera tinctoria ''Indigofera tinctoria'', also called true indigo, is a species of plant from the bean family that was one of the original sources of indigo dye. Description True indigo is a shrub one to two meters high. It may be an annual plant, annual, bi ...
'' and related species were cultivated in
East Asia East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. China, North Korea, South Korea and ...
,
Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Mediter ...
, India, Bangladesh and
Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...
in antiquity. The earliest direct evidence for the use of indigo dates to around 4000 BC and comes from
Huaca Prieta Huaca Prieta is the site of a prehistoric settlement beside the Pacific Ocean in the Chicama Valley, just north of Trujillo, La Libertad Province, Peru. It is a part of the El Brujo Archaeological Complex, which also includes Moche (culture) si ...
, in contemporary Peru.
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 '' ...
mentions India as the source of the dye after which it was named. It was imported from there in small quantities via the
Silk Road The Silk Road () was a network of Eurasian trade routes active from the second century BCE until the mid-15th century. Spanning over 6,400 kilometers (4,000 miles), it played a central role in facilitating economic, cultural, political, and reli ...
. The
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...
term for the dye was ("Indian
dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...
"), which, adopted to
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
(
second declension The second declension is a category of nouns in Latin and Greek with similar case formation. In particular, these nouns are thematic, with an original ''o'' in most of their forms. In Classical Latin, the short ''o'' of the nominative and accusati ...
case) as ''indicum'' or ''indico'' and via
Portuguese Portuguese may refer to: * anything of, from, or related to the country and nation of Portugal ** Portuguese cuisine, traditional foods ** Portuguese language, a Romance language *** Portuguese dialects, variants of the Portuguese language ** Portu ...
, gave rise to the modern word
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 ...
.
Spanish explorers Exploration refers to the historical practice of discovering remote lands. It is studied by geographers and historians. Two major eras of exploration occurred in human history: one of convergence, and one of divergence. The first, covering most ...
discovered an American species of indigo and began to cultivate the product in
Guatemala Guatemala ( ; ), officially the Republic of Guatemala ( es, República de Guatemala, links=no), is a country in Central America. It is bordered to the north and west by Mexico; to the northeast by Belize and the Caribbean; to the east by H ...
. The English and French subsequently began to encourage indigo cultivation in their colonies in the
West Indies The West Indies is a subregion of North America, surrounded by the North Atlantic Ocean and the Caribbean Sea that includes 13 independent island countries and 18 dependencies and other territories in three major archipelagos: the Greater A ...
. In North America, indigo was introduced by
Eliza Lucas Elizabeth "Eliza" Lucas Pinckney (December 28, 1722 May 27, 1793) transformed agriculture in colonial South Carolina, where she developed indigo as one of its most important cash crops. Its cultivation and processing as dye produced one-third the ...
into colonial South Carolina, where it became the colony's second-most important cash crop (after rice). Before the Revolutionary War, indigo accounted for more than one-third of the value of exports from the American colonies. Blue dye can be made from two different types of plants: the indigo plant, which produces the best results, and from the woad plant ''
Isatis tinctoria ''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 ...
'', also known as pastel. For a long time, woad was the main source of blue dye in Europe. Woad was replaced by true indigo as trade routes opened up, and both plant sources have now been largely replaced by
synthetic dyes A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution and ...
.


Classification as a spectral color

The
Early Modern English Early Modern English or Early New English (sometimes abbreviated EModE, EMnE, or ENE) is the stage of the English language from the beginning of the Tudor period to the English Interregnum and Restoration, or from the transition from Middle E ...
word indigo referred to the dye, not to the color (hue) itself, and indigo is not traditionally part of the basic color-naming system. Modern sources place indigo in the
electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from ...
between 420 and 450 nanometers, which lies on the short-wave side of color wheel (RGB) blue, towards (spectral) violet. The correspondence of this definition with colors of actual indigo dyes, though, is disputed. Optical scientists Hardy and Perrin list indigo as between 445 and 464 nm wavelength, which occupies a spectrum segment from roughly the color wheel (RGB) blue extending to the long-wave side, towards azure.
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 ...
introduced indigo as one of the seven base colors of his work. In the mid-1660s, when Newton bought a pair of prisms at a fair near
Cambridge Cambridge ( ) is a university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cambridge bec ...
, the
East India Company The East India Company (EIC) was an English, and later British, joint-stock company founded in 1600 and dissolved in 1874. It was formed to trade in the Indian Ocean region, initially with the East Indies (the Indian subcontinent and Southea ...
had begun importing indigo dye into England, supplanting the homegrown
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 ...
as source of blue dye. In a pivotal experiment in the
history of optics Optics began with the development of lenses by the ancient Egyptians and Mesopotamians, followed by theories on light and vision developed by ancient Greek philosophers, and the development of geometrical optics in the Greco-Roman world. The wo ...
, the young Newton shone a narrow beam of sunlight through a prism to produce a rainbow-like band of colors on the wall. In describing this
optical 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 wavele ...
, Newton acknowledged that the spectrum had a continuum of colors, but named seven: "The originall or primary colours are Red, yellow, Green, Blew, & a violet purple; together with Orang, Indico, & an indefinite varietie of intermediate gradations." He linked the seven prismatic colors to the seven notes of a western
major scale The major scale (or Ionian mode) is one of the most commonly used musical scales, especially in Western music. It is one of the diatonic scales. Like many musical scales, it is made up of seven notes: the eighth duplicates the first at double i ...
, as shown in his color wheel, with orange and indigo as the
semitone A semitone, also called a half step or a half tone, is the smallest musical interval commonly used in Western tonal music, and it is considered the most dissonant when sounded harmonically. It is defined as the interval between two adjacent no ...
s. Having decided upon seven colors, he asked a friend to repeatedly divide up the spectrum that was projected from the prism onto the wall:
I desired a friend to draw with a pencil lines cross the image, or pillar of colours, where every one of the seven aforenamed colours was most full and brisk, and also where he judged the truest confines of them to be, whilst I held the paper so, that the said image might fall within a certain compass marked on it. And this I did, partly because my own eyes are not very critical in distinguishing colours, partly because another, to whom I had not communicated my thoughts about this matter, could have nothing but his eyes to determine his fancy in making those marks.
Indigo is therefore counted as one of the traditional colors of the rainbow, the order of which is given by the mnemonics "Richard of York gave battle in vain" and ''
Roy G. Biv ROYGBIV is an acronym for the sequence of hues commonly described as making up a rainbow: red, orange, yellow, green, blue, indigo, and violet. There are several mnemonics that can be used for remembering this color sequence, such as the ...
''.
James Clerk Maxwell James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and scientist responsible for the classical theory of electromagnetic radiation, which was the first theory to describe electricity, magnetism and ligh ...
and
Hermann von Helmholtz Hermann Ludwig Ferdinand von Helmholtz (31 August 1821 – 8 September 1894) was a German physicist and physician who made significant contributions in several scientific fields, particularly hydrodynamic stability. The Helmholtz Association, ...
accepted indigo as an appropriate name for the color flanking violet in the spectrum. Later scientists concluded that Newton named the colors differently from current usage. According to Gary Waldman, "A careful reading of Newton's work indicates that the color he called indigo, we would normally call blue; his blue is then what we would name
blue-green Blue-green is the color that is between green and blue. It belongs to the cyan family of colors. Variations Cyan (aqua) Cyan, also called aqua, is the blue-green color that is between blue and green on a modern RGB color wheel. The ...
or
cyan Cyan () is the color between green and blue on the visible spectrum of light. It is evoked by light with a predominant wavelength between 490 and 520 nm, between the wavelengths of green and blue. In the subtractive color system, or CMYK color ...
." If this is true, Newton's seven spectral colors would have been: The human eye does not readily differentiate hues in the wavelengths between what are now called blue and violet. If this is where Newton meant indigo to lie, most individuals would have difficulty distinguishing indigo from its neighbors. According to
Isaac Asimov yi, יצחק אזימאװ , birth_date = , birth_place = Petrovichi, Russian SFSR , spouse = , relatives = , children = 2 , death_date = , death_place = Manhattan, New York City, U.S. , nationality = Russian (1920–1922)Soviet (192 ...
, "It is customary to list indigo as a color lying between blue and violet, but it has never seemed to me that indigo is worth the dignity of being considered a separate color. To my eyes, it seems merely deep blue." Modern
color scientists Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associa ...
typically divide the spectrum between violet and blue at about 450 nm, with no indigo.


Distinction among the four major tones of indigo

Like many other colors (
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 * ...
,
rose A rose is either a woody perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred species and tens of thousands of cultivars. They form a group of plants that can be ...
, and
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 ...
are the best-known), indigo gets its name from an object in the natural world—the plant named
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 ...
once used for dyeing cloth (see also
Indigo dye Indigo dye is an organic compound with a distinctive blue color. Historically, indigo was a natural dye extracted from the leaves of some plants of the ''Indigofera'' genus, in particular ''Indigofera tinctoria''; dye-bearing ''Indigofera'' pla ...
). The color "electric indigo" is a bright and
saturated Saturation, saturated, unsaturation or unsaturated may refer to: Chemistry * Saturation, a property of organic compounds referring to carbon-carbon bonds ** Saturated and unsaturated compounds **Degree of unsaturation ** Saturated fat or fatty ac ...
color between the traditional indigo and violet. This is the brightest color indigo that can be approximated on a computer screen; it is a color located between the (primary) blue and the color
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 ...
of the RGB color wheel. The web color blue violet or deep indigo is a tone of indigo brighter than pigment indigo, but not as bright as electric indigo. The color pigment indigo is equivalent to the web color indigo and approximates the color indigo that is usually reproduced in pigments and colored pencils. The color of indigo dye is a different color from either spectrum indigo or pigment indigo. This is the actual color of the dye. A vat full of this dye is a darker color, approximating the web color
midnight blue Midnight blue is a dark shade of blue named for its resemblance to the apparently blue color of a moonlit night sky around full moon. Midnight blue is identifiably blue to the eye in sunlight or full-spectrum light, but can appear black under ...
. Below are displayed these four major tones of indigo.


Electric indigo

"Electric indigo" is brighter than the pigment indigo reproduced below. When plotted on the
CIE chromaticity diagram The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. The mathematical relationships that defin ...
, this color is at 435 nanometers, in the middle of the portion of the spectrum traditionally considered indigo, i.e., between 450 and 420 nanometers. This color is only an approximation of spectral indigo, since actual spectral colors are outside the
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 the
sRGB sRGB is a standard RGB (red, green, blue) color space that HP and Microsoft created cooperatively in 1996 to use on monitors, printers, and the World Wide Web. It was subsequently standardized by the International Electrotechnical Commission ( ...
color system.


Deep indigo (web color blue-violet)

At right is displayed the web color "blue-violet", a color intermediate in brightness between electric indigo and pigment indigo. It is also known as "deep indigo".


Web color indigo

The color box on the right displays the web color indigo, the color indigo as it would be reproduced by artists' paints as opposed to the brighter indigo above (electric indigo) that is possible to reproduce on a computer screen. Its hue is closer to violet than to indigo dye for which the color is named. Pigment indigo can be obtained by mixing 55% pigment cyan with about 45% pigment
magenta Magenta () is a color that is variously defined as pinkish- purplish-red, reddish-purplish-pink or mauvish-crimson. On color wheels of the RGB (additive) and CMY (subtractive) color models, it is located exactly midway between red and blue. I ...
. Compare the subtractive colors to the additive colors in the two primary color charts in the article on
primary colors 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 ...
to see the distinction between electric colors as reproducible from light on a computer screen (additive colors) and the pigment colors reproducible with pigments (subtractive colors); the additive colors are significantly brighter because they are produced from light instead of pigment. Web color indigo represents the way the color indigo was always reproduced in pigments, paints, or colored
pencil A pencil () is a writing or drawing implement with a solid pigment core in a protective casing that reduces the risk of core breakage, and keeps it from marking the user's hand. Pencils create marks by physical abrasion, leaving a trail ...
s in the 1950s. By the 1970s, because of the advent of
psychedelic art Psychedelic art (also known as psychedelia) is art, graphics or visual displays related to or inspired by psychedelic experiences and hallucinations known to follow the ingestion of psychedelic drugs such as LSD, psilocybin, and DMT. The word "p ...
, artists became accustomed to brighter pigments. Pigments called "bright indigo" or "bright blue-violet" (the pigment equivalent of the electric indigo reproduced in the section above) became available in artists' pigments and colored pencils.


Tropical indigo

'Tropical Indigo' is the color that is called ''añil'' in the ''Guía de coloraciones'' (Guide to colorations) by Rosa Gallego and Juan Carlos Sanz, a color dictionary published in 2005 that is widely popular in the
Hispanophone Hispanophone and Hispanic refers to anything relating to the Spanish language (the Hispanosphere). In a cultural, rather than merely linguistic sense, the notion of "Hispanophone" goes further than the above definition. The Hispanic culture is th ...
realm.


Indigo dye

''Indigo dye'' is a greenish dark blue color, obtained from either the leaves of the tropical Indigo plant (''
Indigofera ''Indigofera'' is a large genus of over 750 species of flowering plants belonging to the pea family Fabaceae. They are widely distributed throughout the tropical and subtropical regions of the world. Description Species of ''Indigofera'' are mo ...
''), or from woad (''
Isatis tinctoria ''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 ...
''), or the Chinese indigo ('' Persicaria tinctoria''). Many societies make use of the ''
Indigofera ''Indigofera'' is a large genus of over 750 species of flowering plants belonging to the pea family Fabaceae. They are widely distributed throughout the tropical and subtropical regions of the world. Description Species of ''Indigofera'' are mo ...
'' plant for producing different shades of blue. Cloth that is repeatedly boiled in an indigo dye bath-solution (boiled and left to dry, boiled and left to dry, etc.), the blue pigment becomes darker on the cloth. After dyeing, the cloth is hung in the open air to dry. A Native American woman described the process used by the
Cherokee Indians The Cherokee (; chr, ᎠᏂᏴᏫᏯᎢ, translit=Aniyvwiyaʔi or Anigiduwagi, or chr, ᏣᎳᎩ, links=no, translit=Tsalagi) are one of the indigenous peoples of the Southeastern Woodlands of the United States. Prior to the 18th century, th ...
when extracting the dye:
We raised our indigo which we cut in the morning while the dew was still on it; then we put it in a tub and soaked it overnight, and the next day we foamed it up by beating it with a gourd. We let it stand overnight again, and the next day rubbed
tallow Tallow is a rendering (industrial), rendered form of beef or mutton fat, primarily made up of triglycerides. In industry, tallow is not strictly defined as beef or mutton fat. In this context, tallow is animal fat that conforms to certain techn ...
on our hands to kill the foam. Afterwards, we poured the water off, and the sediment left in the bottom we would pour into a pitcher or crock to let it get dry, and then we would put it into a poke made of cloth (i.e. sack made of coarse cloth) and then when we wanted any of it to dye
here Here is an adverb that means "in, on, or at this place". It may also refer to: Software * Here Technologies, a mapping company * Here WeGo (formerly Here Maps), a mobile app and map website by Here Television * Here TV (formerly "here!"), a TV ...
ith, we would take the dry indigo.
In
Sa Pa Sa Pa (, also written as Sapa) is a district-level town of Lào Cai Province in the Northwest region of Vietnam. As of 2018, the town had a population of 61,498. The town covers an area of 677 km2. The town capital lies at Sa Pa. It is one ...
, Vietnam, the tropical Indigo (''Indigo tinctoria'') leaves are harvested and, while still fresh, placed inside a tub of room-temperature to lukewarm water where they are left to sit for 3 to 4 days and allowed to ferment, until the water turns green. Afterwards, crushed limestone (
pickling lime Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed or slaked with water. It has ma ...
) is added to the water, at which time the water with the leaves are vigorously agitated for 15 to 20 minutes, until the water turns blue. The blue pigment settles as sediment at the bottom of the tub. The sediment is scooped out and stored. When dyeing cloth, the pigment is then boiled in a vat of water; the cloth (usually made from yarns of
hemp Hemp, or industrial hemp, is a botanical class of ''Cannabis sativa'' cultivars grown specifically for industrial or medicinal use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest growing plants o ...
) is inserted into the vat for absorbing the dye. After hanging out to dry, the boiling process is repeated as often as needed to produce a darker color.


Imperial blue


In nature


Birds

* Male
indigobird __NOTOC__ The indigobirds and whydahs, together with the cuckoo-finch, make up the family Viduidae; they are small passerine birds native to Africa. These are finch-like species which usually have black or indigo predominating in their plumage. ...
s are a very dark, metallic blue. * The
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 ...
, native to North America, is mostly bright
cerulean Cerulean (), also spelled caerulean, is a shade of blue ranging between azure and a darker sky blue. The first recorded use of ''cerulean'' as a colour name in English was in 1590. The word is derived from the Latin word '' caeruleus'', "da ...
blue with an indigo head. * The related
blue grosbeak The blue grosbeak (''Passerina caerulea''), is a medium-sized North American passerine bird in the cardinal family Cardinalidae. It is mainly migratory, wintering in Central America and breeding in northern Mexico and the southern United States. ...
is, ironically, more indigo than the indigo bunting.


Fungi

* ''
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 ...
'' is one of the very few species of
mushroom A mushroom or toadstool is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans. The standard for the name "mushroom" is t ...
s colored in tones of blue.


Snakes

* The
eastern indigo snake The eastern indigo snake (''Drymarchon couperi'') is a species of large, non-venomous snake in the family Colubridae. Native to the southeastern region of the United States, it is the longest native snake species in North America. Taxonomy an ...
, ''Drymarchon couperi'', of the southeastern United States, is a dark blue/black.


In culture


Business

*
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 ...
is an Indian budget airline that uses an indigo logo and operates only
Airbus A320 The Airbus A320 family is a series of Narrow-body aircraft, narrow-body airliners developed and produced by Airbus. The A320 was launched in March 1984, Maiden flight, first flew on 22 February 1987, and was introduced in April 1988 by Air F ...
s. *
Indigo Books and Music Indigo Books & Music Inc., known as "Indigo" and stylized "!ndigo", is Canada's only major English-language bookstore chain. It is Canada's largest book, gift, and specialty toy retailer, operating stores in all ten provinces and one terr ...
uses an indigo logo and has sometimes referred to the color as "blue" in advertising. * The
Nintendo GameCube The is a home video game console developed and released by Nintendo in Japan on September 14, 2001, in North America on November 18, 2001, and in PAL territories in 2002. It is the successor to the Nintendo 64 (1996), and predecessor of the Wii ...
was initially released in 2 color varients, including one bearing the title of 'Indigo', featuring the main console and controllers in that color.


Computer graphics

* Electric indigo is sometimes used as a glow color for
computer graphics lighting Computer graphics lighting is the collection of techniques used to simulate light in computer graphics scenes. While lighting techniques offer flexibility in the level of detail and functionality available, they also operate at different levels of ...
, possibly because it seems to change color from indigo to
lavender ''Lavandula'' (common name lavender) is a genus of 47 known species of flowering plants in the mint family, Lamiaceae. It is native to the Old World and is found in Cape Verde and the Canary Islands, and from Europe across to northern and easte ...
when blended with white.


Dyes

* Indigo dye was used to dye denim, giving the original '
blue jeans Jeans are a type of pants or trousers made from denim or dungaree cloth. Often the term "jeans" refers to a particular style of trousers, called "blue jeans", with copper-riveted pockets which were invented by Jacob W. Davis in 1871 and paten ...
' their distinctive colour. *
Guatemala Guatemala ( ; ), officially the Republic of Guatemala ( es, República de Guatemala, links=no), is a country in Central America. It is bordered to the north and west by Mexico; to the northeast by Belize and the Caribbean; to the east by H ...
, as of 1778, was considered one of the world's foremost providers of indigo. * In Mexico, indigo is known as ''añil''. After silver, and
cochineal The cochineal ( , ; ''Dactylopius coccus'') is a scale insect in the suborder Sternorrhyncha, from which the natural dye carmine is derived. A primarily sessility (motility), sessile parasitism, parasite native to tropical and subtropical Sout ...
to produce red, ''añil'' was the most important product exported by historical Mexico. * The use of ''añil'' is survived in the Philippines, particularly in the Visayas and Mindanao. The powder dye is mixed with vinegar to be applied to the cheek of a person suffering from mumps.


Food

* Scientists discovered in 2008 that when a
banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa''. In some countries, bananas used for cooking may be called "plantains", distinguis ...
becomes ripe, it glows bright indigo under a
black light A blacklight, also called a UV-A light, Wood's lamp, or ultraviolet light, is a lamp that emits long-wave (UV-A) ultraviolet light and very little visible light. One type of lamp has a violet filter material, either on the bulb or in a separat ...
. Some insects, as well as birds, see into the
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
, because they are tetrachromats and can use this information to tell when a banana is ready to eat. The glow is the result of a chemical created as the green
chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...
in the peel breaks down.


Literature

Marina Warner's novel ''
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 ...
'' (1992) is a retelling of Shakespeare's '' The Tempest'' and features the production of indigo dye by Sycorax.


Military

The
French Army The French Army, officially known as the Land Army (french: Armée de Terre, ), is the land-based and largest component of the French Armed Forces. It is responsible to the Government of France, along with the other components of the Armed For ...
adopted dark blue indigo at the time of the
French Revolution The French Revolution ( ) was a period of radical political and societal change in France that began with the Estates General of 1789 and ended with the formation of the French Consulate in November 1799. Many of its ideas are considere ...
, as a replacement for the white uniforms previously worn by the Royal infantry regiments. In 1806,
Napoleon Napoleon Bonaparte ; it, Napoleone Bonaparte, ; co, Napulione Buonaparte. (born Napoleone Buonaparte; 15 August 1769 – 5 May 1821), later known by his regnal name Napoleon I, was a French military commander and political leader who ...
decided to restore the white coats because of shortages of
indigo dye Indigo dye is an organic compound with a distinctive blue color. Historically, indigo was a natural dye extracted from the leaves of some plants of the ''Indigofera'' genus, in particular ''Indigofera tinctoria''; dye-bearing ''Indigofera'' pla ...
imposed by the British continental blockade. However, the greater practicability of the blue color led to its retention, and indigo remained the dominant color of French military coats until 1914.


Popular culture

In the ''
Better Call Saul ''Better Call Saul'' is an American crime and legal drama television series created by Vince Gilligan and Peter Gould. Part of the ''Breaking Bad'' franchise, it is a spin-off of Gilligan's previous series, ''Breaking Bad'', and serves as a ...
'' episode "
Hero A hero (feminine: heroine) is a real person or a main fictional character who, in the face of danger, combats adversity through feats of ingenuity, courage, or Physical strength, strength. Like other formerly gender-specific terms (like ...
", Howard Hamlin mentions that his law firm Hamlin Hamlin & McGill trademarked a colour called "Hamlindigo" whilst confronting Jimmy McGill over trademark infringement in a billboard advertisement he produced for his own legal services.


Spirituality

The
spiritualist Spiritualism is the metaphysical school of thought opposing physicalism and also is the category of all spiritual beliefs/views (in monism and dualism) from ancient to modern. In the long nineteenth century The ''long nineteenth century'' i ...
applications use
electric indigo Indigo is a deep color close to the Shades of blue#Blue (RGB) (X11 blue), color wheel blue (a primary color in the RGB color space), as well as to some variants of ultramarine, based on the indigo dye, ancient dye of the same name. The word " ...
, because the color is positioned between
blue 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 of visible light. The eye perceives blue when obs ...
and
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 ...
on the spectrum. * The color electric indigo is used in
New Age New Age is a range of spiritual or religious practices and beliefs which rapidly grew in Western society during the early 1970s. Its highly eclectic and unsystematic structure makes a precise definition difficult. Although many scholars conside ...
philosophy to symbolically represent the sixth ''
chakra Chakras (, ; sa , text=चक्र , translit=cakra , translit-std=IAST , lit=wheel, circle; pi, cakka) are various focal points used in a variety of ancient meditation practices, collectively denominated as Tantra, or the esoteric or ...
'' (called ''
Ajna Ajna ( sa, आज्ञा, IAST: , ), brow or third eye chakra, is the sixth primary chakra in the body according to Hindu tradition and signifies the unconscious mind, the direct link to Brahman (ultimate reality). The third eye is said to ...
''), which is said to include the
third eye The third eye (also called the mind's eye or inner eye) is a mystical invisible eye, usually depicted as located on the forehead, which provides perception beyond ordinary sight. In Hinduism, the third eye refers to the ajna (or brow) chakra. In ...
. This ''chakra'' is believed to be related to
intuition Intuition is the ability to acquire knowledge without recourse to conscious reasoning. Different fields use the word "intuition" in very different ways, including but not limited to: direct access to unconscious knowledge; unconscious cognition; ...
and
gnosis Gnosis is the common Greek noun for knowledge ( γνῶσις, ''gnōsis'', f.). The term was used among various Hellenistic religions and philosophies in the Greco-Roman world. It is best known for its implication within Gnosticism, where it ...
(spiritual knowledge). *
Alice A. Bailey Alice Ann Bailey (June 16, 1880 – December 15, 1949) was a writer of more than twenty-four books on theosophical subjects, and was one of the first writers to use the term New Age. Bailey was born as Alice La Trobe-Bateman, in Manchest ...
used indigo as the "second ray", representing "Love-Wisdom", in her Seven Rays system classifying people into seven metaphysical
psychological type In psychology, personality type refers to the psychological classification of different types of individuals. Personality types are sometimes distinguished from personality traits, with the latter embodying a smaller grouping of behavioral tendenc ...
s. *
Psychic A psychic is a person who claims to use extrasensory perception (ESP) to identify information hidden from the normal senses, particularly involving telepathy or clairvoyance, or who performs acts that are apparently inexplicable by natural laws, ...
s often associate indigo paranormal auras with an interest in
religion Religion is usually defined as a social- cultural system of designated behaviors and practices, morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, or organizations, that generally relates humanity to supernatural, ...
or with intense
spirituality The meaning of ''spirituality'' has developed and expanded over time, and various meanings can be found alongside each other. Traditionally, spirituality referred to a religious process of re-formation which "aims to recover the original shape o ...
and intuition.
Indigo children Indigo children, according to a pseudoscientific New Age concept, are children who are believed to possess special, unusual, and sometimes supernatural traits or abilities. The idea is based on concepts developed in the 1970s by Nancy Ann Tappe, ...
are said to have predominantly indigo auras. People with indigo auras are said to favor occupations such as computer analyst, animal caretaker, and
counselor Counselor or counsellor may refer to: A professional In diplomacy and government * Counsellor of State, senior member of the British royal family to whom the Monarch can delegate some functions in case of unavailability * Counselor (dipl ...
. *In
Wicca Wicca () is a modern Pagan religion. Scholars of religion categorise it as both a new religious movement and as part of the occultist stream of Western esotericism. It was developed in England during the first half of the 20th century and was ...
, it represents emotion, fluidity, insight, and expressiveness. It is used to spiritually heal.


See also

* ''
Baptisia ''Baptisia'' (wild indigo, false indigo) is a genus in the legume family, Fabaceae. They are flowering herbaceous perennial plants with pea-like flowers, followed by pods, which are sometimes inflated. They are native to woodland and grassland in ...
'' (false indigo), a genus of flowering plants *
Champaran Satyagraha The Champaran Satyagraha of 1917 was the first satyagraha movement led by Mahatma Gandhi in British India and is considered a historically important rebellion in the Indian independence movement. It was a farmer's uprising that took place in Ch ...
, the first pacifist rebellion of
Mahatma Gandhi Mohandas Karamchand Gandhi (; ; 2 October 1869 – 30 January 1948), popularly known as Mahatma Gandhi, was an Indian lawyer, anti-colonial nationalist Quote: "... marks Gandhi as a hybrid cosmopolitan figure who transformed ... anti- ...
against the
British Raj The British Raj (; from Hindi ''rāj'': kingdom, realm, state, or empire) was the rule of the British Crown on the Indian subcontinent; * * it is also called Crown rule in India, * * * * or Direct rule in India, * Quote: "Mill, who was himsel ...
* ''
Indigofera ''Indigofera'' is a large genus of over 750 species of flowering plants belonging to the pea family Fabaceae. They are widely distributed throughout the tropical and subtropical regions of the world. Description Species of ''Indigofera'' are mo ...
'', a genus of flowering plants *
Indiglo Indiglo is a product feature on watches marketed by Timex, incorporating an electroluminescent panel as a backlight for even illumination of the watch dial. The brand is owned by Indiglo Corporation, which is in turn solely owned by Timex, an ...
, a brand name for a method of electroluminescence technology *
Lists of colors 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 ...
* '' Persicaria tinctoria'', Japanese Indigo *
Rainbow A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows c ...
, indigo is usually the sixth listed color of the rainbow *
Indigo dye Indigo dye is an organic compound with a distinctive blue color. Historically, indigo was a natural dye extracted from the leaves of some plants of the ''Indigofera'' genus, in particular ''Indigofera tinctoria''; dye-bearing ''Indigofera'' pla ...
, used in dyeing blue jeans their characteristic color


References


External links

* {{Electromagnetic spectrum Tertiary colors Quaternary colors Optical spectrum Rainbow colors Shades of blue