Color Harmony
The idea that some combinations of colour are right and others are not, and that the difference can be stated as a rule. Two centuries of people have tried to write that rule down.
Where the word comes from
Goethe arranged colours in a circle with moral and emotional attributes attached. Chevreul derived harmony from his contrast law. Ostwald and Munsell built solids in which balanced combinations could be found geometrically. Johannes Itten taught seven kinds of contrast at the Bauhaus as a curriculum. Each system is coherent inside itself, and they do not agree with each other — which is the first useful piece of information about colour harmony.
In the studio
The workshops that produced the paintings these systems were built to explain were not pursuing harmony as such. They were working within a palette limited by cost and availability, under a single consistent light, with a patron's instructions about which figure mattered. Unity came out of those constraints rather than out of a scheme. A Baroque picture holds together because six pigments were used everywhere in it, not because the six sat at agreeable angles on a wheel that had not yet been drawn.
Why it matters
Harmony rules describe successful pictures after the fact, and they describe them incompletely. The most memorable colour in painting is frequently the colour that breaks the scheme — the one loud note in a restrained field, the deliberate discord in a van Gogh interior, the single expensive blue in a room of browns. A rule that forbids that note is a rule that would have prevented the painting.
Today
Palette generators now produce harmonies on demand, geometrically, in a second. What they cannot supply is the reason a particular set of colours belongs to a particular thing — which is why generated palettes are usually competent and interchangeable, and why the ones that stay in the memory tend to come with a story attached: a mineral, a place, a period, a specific quality of light.
Pigments used: Ochre · Ultramarine · Bone black
Essays: How colour became a science
See also: Vincent van Gogh · Gustav Klimt · Johannes Vermeer