9. Color nomenclature includes primary, secondary and tertiary colors, and innumerable hues, shades and tints. All these colors bear relations to one another, either relations of analogy, or relations of contrast.
The Circle Diagram I shows the manner in which the various colors are formed.
The third circle shows how slate, citrine and russet are made. For instance, slate is one part of violet and one part of green. Hence, a tertiary color is made of equal parts of two secondaries.
The outer circle, buff, sage and plum, can be analyzed in the same way.
This Diagram I is arranged to show not only component parts of a color, but the parts that properly harmonize.