Note * — Chapter XVIII · On Looking at a Picture

Taking ‘colour’ in this sense to stand for specific colours, not for classes or ranges of varying hues, sets of colours, where in certain spatial proportions and in certain relations of saturation, brightness and luminosity relatively to one another, excite responses of emotion and attitude with marked individual characteristics. Colours, in fact, have harmonic relations, although the physical laws governing these relations are at present unknown, and the relations themselves only imperfectly ascertained. For every colour another can be found such that the combined response to the two will be of a recognisable kind, whose peculiarities are due probably to the compatibility with one another of the impulses set up by each. This compatibility varies in a number of ways. The result is that for every colour a set of other colours is discoverable such that the response to each of them is compatible with the response to the tonic colour in a definite way.* A sensitive colourist feels these compatibilities as giving to these combinations of colours a definite character, which no other combinations possess. Similarly relations of incompatibility between colours can also be felt such that their combination yields no ordered response but merely a clash and confusion of responses. Colours which just fail to be complementary are a typical example. Similarly the primary colours in combination are offensive; should this precise kind of offensiveness be part of the artist’s purpose, he will, of course, make use of them.