I argue that naturalistic pictures provide a guide and a justification for our concept of colour. The crucial relation between pictures and colours is to be brought out, not by reference to the ‘internal’ relations between colours (for example, what differentiates green from red), but by considering how colours are differentiated from the wider range of visually discriminable qualities. Naturalistic pictures effect such a differentiation by simulating colour-like qualities such as gold, amber, and blond, while requiring nothing beyond the three-dimensional (...) manifold of colour space. The seeming simplicity and salience of colour in our visual experience should be recognized as depending on our familiarity with this reductive power of naturalistic pictures. While some sense of these issues has been given expression by many thinkers, the idea is significantly articulated in remarks of Wittgenstein's that were prompted by his reading of a letter the painter Runge wrote to Goethe. (shrink)