Indigo

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Indigo (or spectral indigo) is the color on the spectrum between about 450 and 420 nanometers in wavelength, placing it between blue and violet. Color scientists do not usually recognize indigo as a signficant color category, and classify wavelengths shorter than about 450 nm as violet.^[1]

Indigo and violet are different from purple, which cannot be seen on the electromagnetic spectrum but can be achieved by mixing blue light with red light.

One can see spectral indigo by looking at the reflection of a fluorescent tube in a non-recordable compact disc. This works because the CD functions as a diffraction grating, and a fluorescent lamp generally has a peak at 435.833 nm (from mercury), as is visible on the fluorescent lamp spectrum.

Contents 1 Distinction between four shades of indigo 1.1 Electric indigo 1.2 Deep indigo (web color blue violet) 1.3 Pigment indigo (web color indigo) 1.4 Comparison of blue, indigo, and violet 1.5 Shades of indigo color comparison chart 2 Indigo in human culture 3 See also 4 References

[edit] Distinction between four shades of indigo

Like many other colors (orange and violet are the most well-known), indigo gets its name from an object in the natural world—the plant named indigo once used for dyeing cloth (see also Indigo dye).

The color electric indigo is an approximation of spectrum indigo. This is the color indigo as it can be approximated on a computer screen—it is the color between the web colors blue and violet.

The web color blue violet or deep indigo is a shade 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 than either spectrum indigo or pigment indigo. This is the actual color of the dye from the indigo plant when switched onto raw fabric. A vat full of this dye is a darker color, approximating the web color Midnight Blue.

[edit] Electric indigo

Electric Indigo
— Color coordinates —
Hex triplet		#6600FF
RGBB	(r, g, b)	(102, 0, 255)
HSV	(h, s, v)	(264°, 100%, 100%)
Source		[Unsourced]
B: Normalized to [0–255] (byte)

In an RGB color space, spectral indigo and violet must be approximated by purples, this is, by mixing a little red with a lot of blue. Spectral indigo is closely approximated by the color electric indigo. This sample was taken directly from the CIE chromaticity diagram opposite the 430 nanometer line. It is much brighter than the pigment indigo reproduced below. Spectrum Indigo fits nicely between spectrum violet and spectrum blue as can be seen in the color bands displayed below. It is impossible to represent spectrum indigo exactly on a computer screen, because true spectrum indigo is outside the color triangle or gamut of the RGB color space defined by the monitor primaries.

Indigo is neither an additive primary color nor a subtractive primary color. It was named and defined by Isaac Newton when he divided up the optical spectrum (which is a continuum of frequencies). He specifically named seven colors primarily to match the seven notes of a western major scale, because he believed sound and light were physically similar, but also to link colors with the (known) planets, days of the week, and other lists that had seven items.

Humans do not tend to recognize indigo as a separate hue category between blue and violet. For this reason, some commentators including Isaac Asimov have suggested that indigo should not be regarded as a color in its own right but merely as a shade of blue or violet. Color scientist typically divide the spectrum at about 450 nm between violet and blue, with no indigo.^[1][2]

Others continue to accept it^{[citation needed]} as it has been accepted traditionally as one of Newton's named colors of the spectrum along with red, orange, yellow, green, blue, and violet.

[edit] Deep indigo (web color blue violet)

BlueViolet
— Color coordinates —
Hex triplet		#8A2BE2
RGBB	(r, g, b)	(138, 43, 226)
HSV	(h, s, v)	(271°, 81%, 89%)
Source		[Unsourced]
B: Normalized to [0–255] (byte)

At left is displayed the web color blue violet, a color intermediate in brightness between electric indigo and pigment indigo. This color is also called deep indigo.

[edit] Pigment indigo (web color indigo)

Pigment Indigo
— Color coordinates —
Hex triplet		#4B0082
RGBB	(r, g, b)	(75, 0, 130)
HSV	(h, s, v)	(275°, 100%, 51%)
Source		[Unsourced]
B: Normalized to [0–255] (byte)

The color box at right displays the web color Indigo which is equivalent to pigment indigo, i.e., the color indigo as it would be reproduced by artist's paints as opposed to the brighter indigo above (electric indigo) that it is possible to reproduce on a computer screen.

Pigment indigo is the color you would get to think 55% pigment cyan with about 45% pigment magenta.

Compare the subtractive colors to the additive colors in the two primary color charts in the article on primary colors 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 a lot brighter because they are produced from light instead of pigment.

Pigment indigo (web color indigo) represents the way the color indigo was always reproduced in pigments, paints, or colored pencils in the 1950s. By the 1970s, because of the advent of psychedelic art, artists became used to brighter pigments, and pigments called "bright indigo" or "bright blue-violet" that are the pigment equivalent of the electric indigo reproduced in the section above became available in artists pigments and colored pencils.

[edit] Comparison of blue, indigo, and violet

Note: The spectrum colors can only be approximated on a computer screen due to the color limitations of the color gamut reproducible within the CIE chromaticity diagram.

• blue (Hex: #0000FF) (RGB: 0, 0, 255)
• electric indigo (Hex: #6600FF) (RGB: 102, 0, 255)
• electric violet (Hex: #8B00FF) (RGB: 139, 0, 255)

[edit] Shades of indigo color comparison chart

• lavendula (Vietnamese lavender) (pale indigo) (Hex: #E6E6FA) (RGB: 230, 230, 250)
• periwinkle (lavender blue) (pastel indigo) (Hex: #CCCCFF) (RGB: 204, 204, 255)
• light indigo (Hex: #B198FF) (RGB: 177, 147, 255)
• brilliant indigo (Hex: #9877FF) (RGB: 147, 119, 255)
• steel blue (Hex: #4682B4) (RGB: 70, 130, 180)
• medium Persian blue (Hex: #0067A5) (RGB: 0, 103, 165)
• indigo dye (Hex: #1A5798) (RGB: 17, 80, 147)
• medium indigo (Crayola indigo) (Hex: #4F69C6) (RGB: 79, 105, 198)
• vivid indigo (Hex: #5500FF) (RGB: 85, 0, 255)
• INDIGO (electric indigo) (Hex: #6600FF) (RGB: 102, 0, 255)
• deep indigo (web color blue-violet) (Hex: #8A2BE2) (RGB: 138, 43, 226)
• pigment indigo (web color indigo) (Hex: #4B0082) (RGB: 75, 0, 130)
• Persian indigo (Hex: #32127A) (RGB: 50, 18, 122)
• midnight blue (Hex: #003366) (RGB: 0, 51, 102)
• Prussian blue (Berlin blue) (Hex: #003153) (RGB: 0, 49, 83)
• dark indigo (Hex: #310062) (RGB: 49, 0, 98)

[edit] Indigo in human culture

Computers

• One color of the Apple Computer iMac G3 is indigo.

Food

• The outer skin of many varieties of eggplant is colored pigment indigo.
• So called "purple" carrots and potatoes are actually colored pigment indigo.

Midwifery

• In the ancient Maya civilization indigo was the one color that was recognized for its soothing effect on pregnant women and their unborn children. Pregnant women often wore this color in order to protect themselves and their child from danger and to ensure a safe and successful delivery.

Music

• The Indigo Girls are a folk rock group that is especially popular among lesbians.

New Age Metaphysics

• In the metaphysics of the New Age Prophetess, Alice A. Bailey, in her system called the Seven Rays which classifies humans into seven different metaphysical personality types, the second ray of love-wisdom is represented by the color indigo.
• The Alice A. Bailey books are bound in the color Persian blue, a shade of indigo.

New Age Philosophy

• The color electric indigo is used to symbolically represent the sixth chakra (called Ajna), which is said to include the third eye. This chakra is believed to be related to intuition and gnosis (spiritual knowledge).

Parapsychology

• Psychics who claim to be able to observe the aura with their third eye generally associate indigo, in auras, with an interest in religion or with intense spirituality and intuition. Indigo children are said to have predominately indigo auras.

Video Games

• In keeping with a color theme for towns and cities in Pokémon's Kanto region, the location containing the Elite Four is 'Indigo Plateau.
• The color most associated with the Nintendo Gamecube is a purplish indigo, officially deemed indigo.

[edit] See also

• List of colors
• Indigo dye
• Indiglo, a brand name for a method of electroluminescence technology

[edit] References

					Shades of blue
Alice blue	Azure	Baby blue	Blue	Cerulean	Cerulean blue	Cobalt blue	Cornflower blue	Dark blue	Denim	Dodger blue	Indigo
International Klein Blue	Light blue	Midnight Blue	Navy blue	Periwinkle	Persian blue	Powder blue	Prussian blue	Royal blue	Sapphire	Steel blue	Ultramarine

					Shades of violet
Amethyst	Cerise	Eggplant	Fuchsia	Heliotrope	Indigo	Lavender	Lavender blush	Lavender gray	Lavender rose	Lilac	Magenta
Mauve	Mountbatten pink	Orchid	Palatinate Purple	Persian indigo	Purple	Red-violet	Rose	Sangria	Thistle	Violet	Violet-eggplant
Wisteria
Shades of violet without swatches
Iris	Purpure

v • d • e The Electromagnetic Spectrum
(Sorted by wavelength, short to long) Gamma ray • X-ray • Ultraviolet • Visible spectrum • Infrared • Terahertz radiation • Microwave • Radio waves
Visible (optical) spectrum	Violet • Blue • Green • Yellow • Orange • Red
Microwave spectrum	W band • V band • K band: Ka band, Ku band • X band • C band • S band • L band
Radio spectrum	EHF • SHF • UHF • VHF • HF • MF • LF • VLF • ULF • SLF • ELF
Wavelength designations	Microwave • Shortwave • Mediumwave • Longwave