To avoid blundering with pigment colors, it is well to learn their unbalanced value and chroma, as graphically shown on the opposite page. The central drawing of the Color Tree, and half scale sections in the corners, give a measured model of all color relations.
The upper left-hand diagram is a vertical slice through the neutral axis containing the complementary fields of blue and yellow-red (alias orange). This unbalanced pair may be com- pensated by diminishing either the chroma or the area of yellow-red, as explained in paragraph 77 on page 44. The upper right-hand section contains the complementary fields of yellow and purple-blue which are nearly equal in area, but inverted as to luminosity,—a form of balance suggested in paragraph 76. The lower left-hand diagram gives the complementary fields of purple and green-yellow which are nearly compensated, as are the remaining pair of green and red-purple.
The contour of the central drawing shows the most unbalanced fields of red and its complement blue-green, the latter being but half as strong as red. It is this weak blue-green that limits the size of the color sphere, which may be increased as soon as a reliable blue-green of stronger chroma is available. And here let it be added that different makes of pigment vary considerably, while the output of a single maker may vary from year to year, owing to fluctuations in the color bases, which this measured system will detect and rectify.
The importance of understanding these unbalanced qualities of paint can hardly be overstated, and those who find it difficult to
