Page from A New Practical Treatise on the Three Primitive Colours Assumed as a Perfect System of Rudimentary Information by Charles Hayter
A tertiary color is a color made by mixing full saturation of one primary color with half saturation of another primary color and none of a third primary color, in a given color space such as RGB,CMYK (more modern) or RYB (traditional).
Tertiary colors have specific names, one set of names for the RGB color wheel and a different set for the RYB color wheel. These names are shown below.
The terms for the RYB tertiary colors are not set. For the six RYB hues intermediate between the RYB primary and secondary colors, the names amber/marigold (yellow–orange), vermilion/cinnabar (red–orange), magenta (red–purple), violet (blue–purple), teal/aqua (blue-green), and chartreuse/lime green (yellow–green) are commonly found. The names for the twelve quaternary colors are more variable, if they exist at all, though indigo and scarlet are standard for blue–violet and red–vermilion.
In another sense, a tertiary color is obtained by mixing secondary-colored pigments. These three colors are russet (orange–purple), slate (purple–green), and citron (green–orange), with the corresponding three quaternary colors plum (russet–slate), sage (slate–citron), buff (citron–russet) (with olive sometimes used for either slate or citron). Beyond that are shades of grey (blue grey and brown greys), which approach but never quite reach black.
The RYB color terminology outlined above and in the color samples shown below is ultimately derived from an 1835 book called "Chromatography", an analysis of the RYB color wheel by George Field, a chemist who specialized in pigments and dyes.
RYB colors produced by mixing equal amounts of secondary and subsequent colors
RYB and CMY colors produced by mixing proportional amounts of primary colors
Unlike the RGB (CMY) color wheel, the RYB color wheel has no scientific basis. The RYB color wheel was invented centuries before the 1890s, when it was found by experiment that magenta, yellow, and cyan are the primary colors of pigment, not red, yellow, and blue.
The RGB (CMY) color wheel has largely replaced the traditional RYB color wheel because it is possible to display much brighter and more saturated colors using the primary and secondary colors of the RGB (CMY) color wheel. In the terminology of color theory, RGB color space (CMY color space) has a much larger color gamut than RYB color space.
^William J. Miskella, 1928, Practical Color Simplified: A Handbook on Lacquering, Enameling, Coloring And Painting, pp
^John Lemos, 1920, "Color Charts for the School Room", in School Arts, vol. 19, pp 580–584
^Maerz and Paul A Dictionary of Color New York:1930 Page 154
^ abcRGB approximations of RYB tertiary colors, using cubic interpolation. The colors are paler than a simple mixture of paints would produce. For the darker, true secondary colors, see secondary color. Pure tertiary colors would be darker still.