A common list identifies six main bands: red, orange, yellow, green, blue, and violet. The color table should not be interpreted as a definitive list-the pure spectral colors form a continuous spectrum, and how it is divided into distinct colors linguistically is a matter of culture and historical contingency (although people everywhere have been shown to perceive colors in the same way). The wavelengths listed are as measured in air or vacuum (see refractive index). The table at right shows approximate frequencies (in terahertz) and wavelengths (in nanometers) for various pure spectral colors. The familiar colors of the rainbow in the spectrum-named using the Latin word for appearance or apparition by Isaac Newton in 1671-include all those colors that can be produced by visible light of a single wavelength only, the pure spectral or monochromatic colors. This effect can be visualized by comparing the light sources' spectral power distributions and the resulting colors. In each such class the members are called metamers of the color in question. In fact, one may formally define a color as a class of spectra that give rise to the same color sensation, although such classes would vary widely among different species, and to a lesser extent among individuals within the same species. Although the spectrum of light arriving at the eye from a given direction determines the color sensation in that direction, there are many more possible spectral combinations than color sensations. Most light sources emit light at many different wavelengths a source's spectrum is a distribution giving its intensity at each wavelength. When the wavelength is within the visible spectrum (the range of wavelengths humans can perceive, approximately from 390 nm to 700 nm), it is known as "visible light". The saturation of a color a measurement of how close a color is to gray.Įlectromagnetic radiation is characterized by its wavelength (or frequency) and its intensity.
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