14. The harmony of contrast consists of colors in no way related. As an example of the harmony of analogy, we would mention red and orange, because both of these colors have ingredients in common, red being one of the two component parts of orange. As an example of the harmony of contrast, we suggest red and green, because there is nothing in common between the two, red being a primary color, and green a secondary, composed of the other two primaries, yellow and blue. (See [¶ 17].)
15. Green is called the complement of red. The complement of blue would be orange, because orange is formed by combining the remaining primaries, red and yellow; and the complement of yellow would be violet, because violet is composed of blue and red, the other primaries.
16. In [Diagram II] we have arranged at opposite points the primaries 1, the secondaries 2, the tertiaries 3, the quaternaries 4.
But [Diagram III] goes further into the subject.
It is easy to understand the composition of secondaries, but it is not so easy to know the tertiaries and quaternaries. (See also [Diagram I].)
CONTRAST ANALOGIES
17. [Diagram III] is of the utmost value to the colorist, illustrating not only the composition of color, but showing the origin of each secondary from the two primaries, the origin of each tertiary from two secondaries, and of each quaternary from two tertiaries. It shows by groupings the harmonies of analogy or related colors; also the harmonies of contrast: By moving on the board one color on one line to another color upon another line, like the moving of a knight in a game of chess, and confining the moves always to adjoining lines, like yellow to violet, violet to citrine, citrine to plum, plum to brown. Yellow and violet are true contrasts, the one color having nothing in common with the other. The citrine and the plum, however, are approximate contrasts. For greater convenience, we have numbered the contrasting colors A’s and B’s. Absolute contrast is where the two colors have nothing in common. For composition purposes, however, citrine and violet may be considered contrasts, or correctly speaking, contrast analogies. (See [¶ 19].)
18. A harmony of contrast means the utilization of a primary color with its complementary, or a color in conjunction with another color in no degree related: a primary with a secondary. But when we soften these contrasting colors by the addition of white we have in the lighter tints a scale of chroma that is a form of analogy.