Every colour system begins with the same act: bending the rainbow into a circle. Red shades into orange, orange into yellow, and at the far end violet reaches back toward red — a closed loop with no first colour and no last.
This wheel has twenty-four steps, the count used by the Japanese Practical Color Co-ordinate System. Each wedge carries the book’s strongest pigment at that hue; the faint wedges are hues the book left unmixed.
Stare at a red square for thirty seconds, then look at white paper: a green square appears. Every colour leaves an afterimage, and the afterimage is a specific second colour. This circle is arranged so that those pairs sit directly across from each other.
A circle is not enough. Two colours can share a hue and differ in everything else. The second dimension is value: how light or dark a colour is, independent of what hue it carries.
Albert Munsell, a Boston painter, built his system on this axis in 1905. His ladder runs from black at 0 to white at 10, and each rung is spaced by eye, not by instrument — equal steps of seeing.
Combination № 165: one red family at three heights — Cameo Pink, Spinel Red, Vistoris Lake. Beside them, the same three chips with hue removed. The gray column is what value measures: what survives when colour is taken away.
The third dimension runs outward. Chroma is distance from gray: at zero the colour is gray; each step outward, the hue strengthens.
The arms have different lengths. The book’s strongest red, Spectrum Red, reaches chroma 17; its strongest blue-green, Sea Green, stops at 8. Munsell built his model as a tree and let the branches stay unequal — each arm sits at the value where its hue peaks, and runs as far as the hue can go.
Three dimensions are true, but clumsy in the hand. In 1964 the Japan Color Research Institute folded two of them together. Value and chroma, taken as one, become tone: pale, soft, dull, deep, vivid, dark — words a designer already thinks in.
A colour is then just two coordinates: which hue, what tone. This is the PCCS — and the reason a whole wheel can be held as a single disc with a tone written on its rim.
Lay Wada’s pigments on the tone chart and his taste appears as geography: crowds in some regions, thin air in others.
Harmony, in every classical account, is an interval — not the colours themselves but the distance between them. Opposite on the wheel: complementary. A third of the circle apart: a triad. Next-door neighbours: analogous.
The old paper calculators cut these intervals as windows in a mask. Lay the mask on the wheel, turn it, and every position asks the same question with a different subject.
Sort the 348 combinations by their widest hue interval. 166 — nearly half the book — reach fully across the wheel; only 48 stay among neighbouring hues. Even in the widest rows, soft weights outnumber vivid ones: light and pale are their two most common tones.
The dictionary and the tone system share an author. Sanzo Wada — painter, costume designer, an Academy Award for Gate of Hell — published the dictionary in the 1930s. In 1945 he reorganised Japan’s colour standards body and led it as the Japan Color Research Institute; in 1964 that institute published the tone system taught in these chapters. His taste came first, then his measure of it.