Additive primary colors

A set of primary colors is a set of pigments, colored lights, or abstract elements of a mathematical color space model that can be combined in varying amounts to produce a range or "gamut" of colors. Deriving many colors from several primaries facilitates technological and artistic applications such as painting, electronic displays, and printing. Any small set of realizable primary colors are "imperfect" in that they cannot generate all perceptible colors, but some sets of primaries can yield a far wider gamut than others.

For an additive set of primary colors for human vision, as in a television or computer display screen, projector, or other emissive electronic visual displays, the usual choice is red, green, and blue (RGB), although the primaries' specific chromaticities can vary.

For a set of subtractive primary colors for humans, as in mixing of pigments for printing, cyan (a bright greenish-blue), magenta (a bright reddish purple), and yellow are often used (usually supplemented by black to make CMYK).

Red, yellow, and blue (RYB) are a well-known traditional set of subtractive primaries in the art field. Artists often use more than three chromatic pigments and so are not limited to a colorspace such as RYB even if they think of these three as their primary colors in an abstract or conceptual sense, for example when constructing a color wheel.

The precise set of primary colors to be used in a specific color application depends on gamut requirements as well as on application-specific constraints such as cost, power consumption, lightfastness, mixing behavior, etc.

Abstract colorspaces include the additive CIE XYZ, in which all visible colors can be represented mathematically by combinations of its X, Y, and Z primaries, but each primary itself does not directly correspond to a physically-possible light source.

The response of the eye to a "mix" of primary colors is predicted by different models for different applications.

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