Complete the account of contrast.

Chevreul published his law of simultaneous contrast in 1839, after work at the Gobelins tapestry manufactory. Josef Albers set out the same effects as a teaching method in Interaction of Color in 1963. The change in a whole repeating pattern caused by altering one of its colours is called the Bezold effect.

The two dates bracket the subject: an industrial chemist working out why a black looked wrong, and a painter turning the same effect into an exercise book that still sells. Between them sits Bezold, whose contribution is that the effect is not local, one colour changed alters the reading of a whole field.