Colors may be grouped to please or to give annoyance.
[(146)] Attempts to define the laws of harmonious color have not attained marked success, and the cause is not far to seek. The very sensations underlying these effects of concord or of discord are themselves undefined. The misleading formula of my student days—that three parts of yellow, five parts of red, and eight parts of blue would combine harmoniously—was unable to define the kind of red, yellow, and blue intended; that is, the hue, value, and chroma of each of these colors was unknown, and the formula meant a different thing to each person who tried to use it.
[(147)] It is true that a certain red, green, and blue can be united in such proportions on Maxwell discs as to balance in a neutral gray; but the slightest change in either the hue, value, or chroma, of any one of them, upsets the balance. A new proportion is then needed to regain the neutral mixture. This has already been shown in the discussion of triple balance (paragraph [82]).
[(148)] Harmony of color has been still further complicated by the use of terms that belong to musical harmony. Now music is a measured art, and has found a set of intervals which are defined scientifically. The two arts have many points of similarity; and the impulses of sound waves on the ear, like those of light waves on the eye, are measured vibrations. But they are far apart in their scales, and differ so much in important particulars that no practical relationship can be set up. The intervals of color sensation require fit names and measures, ere their infinite variety can be organized into a fixed system.
[(149)] Any effort to compare certain sounds to certain colors soon leads to the wildest vagaries.
Harmony of sound is unlike harmony of color.
[(150)] The poverty of color language tempts to a borrowing from the richer terminology of music. Musical terms, such as “pitch, key, note, tone, chord, modulation, nocturne, and symphony,” are frequently used in the description of color, serving by association to convey certain vague ideas.
[(151)] In the same way the term color harmony, from association with musical harmony, presents to the mind an image of color arrangement,—varied, yet well proportioned, grouped in orderly fashion, and agreeable to the eye. But any attempt to define this image in terms of color is disappointing. Here is a beautiful Persian rug: why do we call it beautiful? One says “because its colors are rich.” Why are they rich? “Because they are deep in tone.” What does that mean? The double-bass and the fog-horn are deep in tone, but not necessarily beautiful on that account. “Oh, no,” says another, “it is all in one harmonious key.” But what is a key of color? Is it made by all the values of one color, such as red, or by all the hues of equal value, such as the middle hues in our color solid?
[(152)] Certainly it is neither, for the rug has both light and dark colors; and, of the reds, yellows, greens, and blues, some are stronger and others weaker. Then what do we mean by a key of color? One must either continue to flounder about or frankly confess ignorance.
[(153)] Musical harmony explains itself in clear language. It is illustrated by fixed and definite sound intervals, whose measured relations form the basis of musical composition. Each key has an unmistakable character, and the written score presents a statement that means practically the same thing to every person of musical intelligence. But the adequate terms of color harmony are yet to be worked out.