Spectral color

A spectral color is a color that is evoked by a single wavelength of light in the visible spectrum, or by a relatively narrow band of wavelengths, also known as monochromatic light. Every wavelength of light is perceived as a spectral color, in a continuous spectrum; the colors of sufficiently close wavelengths are indistinguishable.

The spectrum is often divided up into named colors, though any division is somewhat arbitrary: the spectrum is continuous. Traditional colors include: red, orange, yellow, green, blue, and violet.

The division used by Isaac Newton, in his color wheel, was: red, orange, yellow, green, blue, indigo and violet; a mnemonic for this order is "Roy G. Biv". In modern divisions of the spectrum, indigo is often omitted; see indigo#Classification as a spectral color for details.

One needs at least trichromatic color vision for there to be a distinction between spectral and non-spectral colours: trichromacy gives a possibility to perceive both hue and saturation in the chroma. In color models capable to represent spectral colors, such as CIELUV, a spectral color has the maximal saturation among all colors of the same hue.