Most color terms are borrowed from other senses.
[(6)] When his older sister refers to the “tone” of her green dress, or speaks of the “key of color” in a picture, he is naturally confused, because tone and key are terms associated in his mind with music. It may not be long before he will hear that “a color note has been pitched too high,” or that a certain artist “paints in a minor key.” All these terms lead to mixed and indefinite ideas, and leave him unequipped for the clear expression of color qualities.
[(7)] Musical art is not so handicapped. It has an established scale with measured intervals and definite terms. Likewise, coloristic art must establish a scale, measure its intervals, and name its qualities in unmistakable fashion.
Color has three dimensions.
[(8)] It may sound strange to say that color has three dimensions, but it is easily proved by the fact that each of them can be measured. Thus in the case of the boy’s faded cap its redness or HUE[3] is determined by one instrument; the amount of light in the red, which is its VALUE,[3] is found by another instrument; while still a third instrument determines the purity or CHROMA[3] of the red.
The omission of any one of these three qualities leaves us in doubt as to the character of a color, just as truly as the character of this studio would remain undefined if the length were omitted and we described it as 22 feet wide by 14 feet high. The imagination would be free to ascribe any length it chose, from 25 to 100 feet. This length might be differently conceived by every individual who tried to supply the missing factor.
[(10)] The fruit is then filled with assorted colors, graded from white to black, according to their VALUES, and disposed by their HUES in the five sections. A slice near the top will uncover light values in all hues, and a slice near the bottom will find dark values in the same hues. A slice across the middle discloses a circuit of hues all of MIDDLE VALUE; that is, midway between the extremes of white and black.
[(11)] Two color dimensions are thus shown in the orange, and it remains to exhibit the third, which is called CHROMA, or strength of color. To do this, we have only to take each section in turn, and, without disturbing the values already assorted, shove the grayest in toward the narrow edge, and grade outward to the purest on the surface. Each slice across the fruit still shows the circuit of hues in one uniform value; but the strong chromas are at the outside, while grayer and grayer chromas make a gradation inward to neutral gray at the centre, where all trace of color disappears. The thin edges of all sections unite in a scale of gray from black to white, no matter what hue each contains.