Primary Colors

Almost all visible colors can be obtained by the additive color mixing of three colors that are in widely spaced regions of the visible spectrum. If the three colors of light can be mixed to produce white, they are called primary colors and the standard additive primary colors are red, green and blue.

Two colors that produce white when added together are called complementary. The color complementary to a primary color is called a secondary color. The complementary or secondary colors for red, green and blue are cyan, magenta and yellow respectively. These three colors are often referred to as the subtractive primary colors. When the three are combined in subtractive color mixing, they produce black.




Primary colors are sets of colors that can be combined to make a useful range of colors. For human applications, three primary colors are usually used, since human color vision is trichromatic.
For additive combination of colors, as in overlapping projected lights or in CRT displays, the primary colors normally used are red, green, and blue. For subtractive combination of colors, as in mixing of pigments or dyes, such as in printing, the primaries normally used are cyan, magenta, and yellow, though the set of red, yellow, blue is popular among artists. See RGB color model, CMYK color model, and RYB color model for more on these popular sets of primary colors.
Any choice of primary colors is essentially arbitrary; for example, an early color photographic process, autochrome, typically used orange, green, and violet primaries. However, unless negative amounts of a color are allowed the gamut will be restricted by the choice of primaries.
The combination of any two primary colors creates a secondary color.
The most commonly used additive color primaries are the secondary colors of the most commonly used subtractive color primaries, and vice versa.




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