[(75)] This raises the question, What is balance of color? Artists criticise the color schemes of paintings as being “too light or too dark” (unbalanced in value), “too weak or too strong” (unbalanced in chroma), and “too hot or too cold” (unbalanced in hue), showing that this is a fundamental idea underlying all color arrangements.
[(76)] Let us assume that the centre of the sphere is the natural balancing point for all colors (which will be best shown by Maxwell discs in Chapter V., paragraphs [106–112]), then color points equally removed from the centre must balance one another. Thus white balances black. Lighter red balances darker blue-green. Middle red balances middle blue-green. In short, every straight line through this centre indicates opposite qualities that balance one another. The color points so found are said to be “complementary,” for each supplies what is needed to complement or balance the other in hue, value, and chroma.
[(77)] The true complement of the buttercup, then, is not the violet, which is too weak in chroma to balance its strong opposite. We have no blue flower that can equal the chroma of the buttercup. Some other means must be found to produce a balance. One way is to use more of the weaker color. Thus we can make a bunch of buttercups and violets, using twice as many of the latter, so that the eye sees an area of blue twice as great as the area of yellow-red. Area as a compensation for inequalities of hue, value, and chroma will be further described under the harmony of color in [Chapter VII.]
[(78)] But, before leaving this illustration of the buttercup and violet, it is well to consider another color path connecting them which does not pass through the sphere, but around it (Fig. 12). Such a path swinging around from yellow-red to blue slants downward in value, and passes through yellow, green-yellow, green, and blue-green, tracing a sequence of hue, of which each step is less chromatic than its predecessor.
This diminishing sequence is easily written thus,—YR8/9, Y7/8, GY6/7, G5/6, BG4/5, B3/4,—and is shown graphically in Fig. 12. Its hue sequence is described by the initials YR, Y, GY, G, BG, and B. Its value-sequence appears in the upper numerals, 8, 7, 6, 5, 4, and 3, while the chroma-sequence is included in the lower numerals, 9, 8, 7, 6, 5, and 4. This gives a complete statement of the sequence, defining its peculiarity, that at each change of hue there is a regular decrease of value and chroma. Nature seems to be partial to this sequence, constantly reiterating it in yellow flowers with their darker green leaves and underlying shadows. In spring time she may contract its range, making the blue more green and the yellow less red, but in autumn she seems to widen the range, presenting strong contrasts of yellow-red and purple-blue.
[(79)] Every day she plays upon the values of this sequence, from the strong contrasts of light and shadow at noon to the hardly perceptible differences at twilight. The chroma of this sequence expands during the summer to strong colors, and contracts in winter to grays. Indeed, Nature, who would seem to be the source of our notions of color harmony, rarely repeats herself, yet is endlessly balancing inequalities of hue, value, and chroma by compensations of quantity.
[(80)] So subtle is this equilibrium that it is taken for granted and forgotten, except when some violent disturbance disarranges it, such as an earthquake or a thunder-storm.
The triple nature of color balance illustrated.
[(81)] The simplest idea of balance is the equilibrium of two halves of a stick supported at its middle point. If one end is heavier than the other, the support must be moved nearer to that end.