"Unlike the essentially naturalistic colour opposition of yellow-blue/violet which characterized the Impressionist colour, Matisse began to exploit the more abstract, and... vibrant, oppositions of red-green. Because red and green colours are the closest in tone of all the complementary colour pairs, they set up a dazzling sensation which gives its own light and brilliance, without any direct imitation of natural effects of light. Thus the properties of colour itself, and the interactions of colour... were the basis of Matisse's mature art. Colour no longer stood for, or symbolized, anything external to painting itself; it was colour as colour."