For Knight, colour is experienced directly as pleasurable sensation. A pure blue is not pleasurable because it reminds us of clear skies, as Price supposed, but because of the experience itself. Interpretation of impressions follows chains of association following from this primal sensory experience. However, the pleasures of sense may be 'modified by habit', so that the pure stimulus of colour may be experienced as pleasurable when 'under the influence of mind' which perceives its meaningful use within a painting. Excess of pure colour is painful, like any other sensory excess. Variety and combination of colours is most pleasurable.