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 the 1835 book Chromatography, an analysis of the RYB color wheel by George Field, a chemist who specialized in pigments and dyes. See also Color wheel Color theory References Tertiary colors