n becomes refined by exercise, and, when a child tries to
imitate the subtle colors of nature with paints, he begins to realize
that the strongest colors are not the most beautiful,--rather the
tempered ones, which may be compared to the moderate sounds in music. To
describe these tempered colors, he must estimate their hue, value, and
chroma, and be able to describe in what degree his copy departs from the
natural color. And, with this gain in perception and imitation of
natural color, he finds a strong desire to invent combinations to please
his fancy. Thus the study divides into three related attitudes, which
may be called recognition, imitation, and invention. Recognition of
color is fundamental, but it would be tedious to spend a year or two in
formal and dry exercises to train recognition of color alone; for each
step in recognition of color is best tested by exercise in its imitation
and arrangement. When perception becomes keener, emphasis can be placed
on imitation of the colors found in art and in nature, resting finally
on the selection and grouping of colors for design.[13]

[Footnote 13: See Course of Study, Part II.]

+Every color can be recognized, named, matched, imitated, and written
by its HUE, VALUE, and CHROMA.+

(40) The notation used in this system places Hue (expressed by an
initial) at the left; Value (expressed by a number) at the right and
above a line; and Chroma (also expressed by a number) at the right,
below the line. Thus R 5/9 means HUE (red), VALUE (5)/CHROMA (9), and
will be found to represent the qualities of the pigment vermilion.[14]

[Footnote 14: See Chapter VI.]

Hue, value, and chroma unite in every color sensation, but the child
cannot grasp them all at once. _Hue-difference appeals to him first_,
and he gains a permanent idea of five principal hues from the enamels of
MIDDLE COLORS, learning to name, match, imitate, and finally write them
by their initials: R (red), Y (yellow), G (green), B (blue), and P
(purple). Intermediates formed by uniting successive pairs are also
written by the joined initials, YR (yellow-red), GY (green-yellow), BG
(blue-green), PB (purple-blue), and RP (red-purple).

(41) Ten differences of hue are as many as a child can render at the
outset, yet in matching and imitating them he becomes aware of their
light and dark quality, and learns to separate it from hue as
_value-difference_. Middle colors, as implied by that name, stand midway