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Is it possible to define the endless varieties of color?

(30) At first glance it would seem almost hopeless to attempt the naming of every kind and degree of color. But, if all these varieties possess the same three qualities, only in different degrees, and if each quality can be measured by a scale, then there is a clue to this labyrinth.

A COLOR SPHERE and COLOR TREE to unite hue, value, and chroma.

(31) This clue is found in the union of these three qualities by measured scales in a color sphere and color tree.[1] The equator An image should appear at this position in the text. of the sphere[2] may be divided into ten parts, and serve as the scale of hue, marked R, YR, Y, GY, G,.BG, B, PB, P; and P: Its vertical axis may be divided into ten parts to serve as the scale of value, numbered from black (0) to white (10). Any perpendicular to the neutral axis is ascale of chroma. On the plane of the equator this scale is numbered 1, 2, 3, 4, 5, from the centre to the surface.

(32) This chroma scale may be raised or lowered to any level of value, always remaining perpendicular to the axis, and serv- ing to measure the chroma of every hue at every level of value. The fact that some colors exceed others to such an extent as to carry them out beyond the sphere is proved by measuring instru-

  1. See Color Tree in paragraph 14.
  2. Unaware that the spherical arrangement had been used years before, I devised a double tetrahedron to classify colors, while a student of painting in 1879. It now appears that the sphere was common property with psychologists, having been described by Runge in 1810. Earlier still, Lambert had suggested a pyramidal form. Both are based on the erroneous assumption that red, yellow, and blue are primary sensations, and also fail to place these hues in a just scale of luminosity. My twirling color solid and its completer development in the present model have always made prominent the artistic feeling for color value. It differs in this and in other ways from previous systems, and is fortunate in possessing new apparatus to measure the degree of hue, value, and chroma.