Indigo

From Encyclopedia Jr, free information reference for Kids

This article is about the color. For other uses, see Indigo (disambiguation).

Indigo (or spectral indigo) is the color on the spectrum between 440 and 420 nanometres in wavelength, placing it between blue and violet. Indigo and violet are different from purple (as defined by chromaticians [color scientists]) which does not exist on the electromagnetic spectrum and which can be achieved using additive primary colors by mixing blue light with a 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.

1 Distinction between four shades of indigo
2 Indigo in culture
3 See also

[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 is the color indigo as it looks reproduced on a computer screen--it is the color between the web color blue and the color violet.

The web color blue violet or bright indigo is a shade of indigo brighter than pigment indigo but not as bright as electic indigo.

The color pigment indigo is equivalent to the web color indigo and is the color indigo that is usually reproduced in pigments and colored pencils. (Electric indigo can be reproduced approximately in pigments, but it requires adding some white pigment to pigment indigo.)

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 swatched onto raw fabric. A vat full of this dye is a darker color, approximating the web color Midnight Blue.

When referring to the color Indigo it is always necessary to specify which of the four colors all called indigo you are referring to: the color electric indigo, the color blue-violet (bright indigo), the color pigment indigo, or the color indigo dye (they are four entirely separate and distinct colors).

[edit] Electric indigo

Electric Indigo
— Color coordinates —
Hex triplet		#6600FF
RGB^B	(r, g, b)	(102, 0, 255)
CMYK^H	(c, m, y, k)	(, , , )
HSV	(h, s, v)	({{{h}}}°, %, %)
B: Normalized to [0–255] (byte) H: Normalized to [0–100] (hundred)

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. This color is the approximation of spectrum indigo on a computer screen. It is impossible to represent spectrum indigo exactly on a computer screen, because true spectrum indigo is outside the gamut of the CIE chromaticity diagram, but electric indigo is a close approximation.

In the psychedelic 1960s, electric indigo color would have been approximated by mixing some fluorescent magenta pigment with a larger amount of fluorescent blue pigment.

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 musical scale, because he believed sound and light were physically similar, but also to link colours with the (known) planets, days of the week, and other lists that had seven items.

The human eye is relatively insensitive to indigo's frequencies, and some otherwise well-sighted people cannot distinguish indigo from 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.

Others continue to accept it as it has been accepted traditionally as one of the major colors of the spectrum along with red, orange, yellow, green, blue, and violet. By looking at the color band comparison chart below of the three colors blue, indigo, and violet, anyone with normal color vision can easily see that all three of these colors are quite distinct.

Of all the pure chromas, indigo has what chromaticians call the highest value, i.e., indigo is intrinsically the darkest of the colors on the color wheel, just as yellow has the lowest value of all the colors on the color wheel, i.e., yellow is the lightest pure chroma on the color wheel.

[edit] Bright indigo (web color blue violet)

BlueViolet
— Color coordinates —
Hex triplet		#8A2BE2
RGB^B	(r, g, b)	(138, 43, 226)
CMYK^H	(c, m, y, k)	(, , , )
HSV	(h, s, v)	({{{h}}}°, %, %)
B: Normalized to [0–255] (byte) H: Normalized to [0–100] (hundred)

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 bright indigo.

[edit] Pigment indigo (web color indigo)

Indigo (closest in gamut)
— Color coordinates —
Hex triplet		#4B0082
RGB^B	(r, g, b)	(75, 0, 130)
CMYK^H	(c, m, y, k)	(42, 100, 0, 49)
HSV	(h, s, v)	(275°, 100%, 51%)
B: Normalized to [0–255] (byte) H: Normalized to [0–100] (hundred)

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 if you mixed about 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] Indigo dye

Indigo dye
— Color coordinates —
Hex triplet		#1A5798
RGB^B	(r, g, b)	(17, 80, 147)
CMYK^H	(c, m, y, k)	(77, 17, 0, 27)
HSV	(h, s, v)	(275°, 50%, 51%)
B: Normalized to [0–255] (byte) H: Normalized to [0–100] (hundred)

Displayed at right is the color indigo dye. This color sample was taken directly from the indigo dye color swatch in the Encyclopedia Jr Indigo dye article. A vat full of indigo dye would be a much darker color, approximating the web color midnight blue.

[edit] Comparison of electric indigo, bright indigo, pigment indigo, indigo dye, and midnight blue

electric indigo (Hex: #6600FF) (RGB: 102, 0, 255)
bright indigo (web color blue-violet) (Hex: #8A2BE2) (RGB: 138, 43, 226)
pigment indigo (Hex: #4B0082) (RGB: 75, 0, 130)
indigo dye (Hex: #1A5798) (RGB: 17, 80, 147)
midnight blue (Prussian blue) (Hex: #003366) (RGB: 0, 51, 102)

[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] Indigo in culture

Food

The outer skin of most 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.

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 related to intuition and knowledge.

New Age Psychology Parapsychology

Psychics who claim to be able to observe the aura with their third eye generally regard someone with an indigo aura as being someone who is religious and intuitive. It is also predominant in the aura of the indigo children.

[edit] See also

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

					Shades of blue
Alice blue	Azure	Blue	Cerulean	Cerulean blue	Cobalt blue	Cornflower blue	Dark blue	Denim	Dodger blue	Indigo	International Klein Blue

Lavender	Midnight Blue	Navy blue	Periwinkle	Persian blue	Powder blue	Prussian blue	Royal blue	Sapphire	Steel blue	Ultramarine	Light blue

					Shades of violet
Amethyst	Cerise	Eggplant	Fuchsia	Heliotrope	Indigo	Lavender	Lavender Blush	Lilac	Magenta	Mauve	Mountbatten pink

Orchid	Persian indigo	Purple	Red-violet	Sangria	Thistle	Violet	Violet-eggplant	Wisteria	Rose

Shades of violet without swatches
Iris	Palatinate	Purpure

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: K_a band, K_u 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

Categories: Shades of blue | Shades of violet | Optical spectrum