Colour-Control

Fletcher's starting point was a practical problem: modern pigments gave painters far more range than the eye could sensibly carry on one palette at once, yet a permanently fixed set of colours was too narrow for every subject. His answer, borrowed loosely from musical key-signatures, was to build each palette from a key-note and a fixed sequence of unequal steps around the hue circle, rather than picking colours by eye.

Twelve hues sit evenly around the wheel. From any key-note, a triad is built using uneven spacing rather than an even split: this avoids landing on a direct complementary pair while still keeping real variety and one pair of hues in close, lively contrast. All six points, Key, C1, C2, 4th, 5th and 6th, can each be switched on or off independently under Palette points, so you can work from a single hue up to the full six in whatever combination a scenario calls for. The Triad button above them is a shortcut back to the classic three-colour key (Key, C1, C2): it's on by default, and drops out again as soon as you start toggling individual points.

The wheel's rings move from full intensity at the rim to neutral at the centre in twenty graded steps, echoing Fletcher's own idea that distance from the middle of the wheel stands for a colour's intensity, with the raw neutral shown as a solid disc at the very centre. The Value and Chroma sliders shift that whole wheel lighter/darker and more/less saturated, so you can tune a key to a particular light before reading off hex values.

The interval pattern, the twelve base pigments, and the grading strip are all defined near the top of this page's script, so the system can be adjusted to a different version without touching the drawing logic.