Color triangle

A color triangle is an arrangement of colors within a triangle, based on the additive or subtractive combination of three primary colors at its corners.

An additive color space defined by three primary colors has a chromaticity gamut that is a color triangle, when the amounts of the primaries are constrained to be nonnegative.

Before the theory of additive color was proposed by Thomas Young and further developed by James Clerk Maxwell and Hermann von Helmholtz, triangles were also used to organize colors, for example around a system of red, yellow, and blue primary colors.

After the development of the CIE system, color triangles were used as chromaticity diagrams, including briefly with the trilinear coordinates representing the chromaticity values. Since the sum of the three chromaticity values has a fixed value, it suffices to depict only two of the three values, using Cartesian co-ordinates. In the modern x, y diagram, the large triangle bounded by the imaginary primaries X, Y, and Z has corners (1, 0), (0, 1), and (0, 0), respectively; color triangles with real primaries are often shown within this space.

If the colors of the chromaticity diagram are inverted, a triangle with real primary colors cyan, magenta, and yellow at its corners, and black at its center, can be outlined within it, representing a modern understanding of subtractive color mixing that is useful for dye- or pigment-based media such as paint or ink. Secondaries red, blue, and green then lie along the sides of the triangle, representing mixtures made from the colors at adjacent corners. The black center represents the darkening that occurs when all three primaries, or any two complementary colors, are mixed.