The old port at Collioure is still a popular place for painters, who set up their easels in the shade of the dense green foliage of a row of very large, old plane trees and look out at the brilliant view of Mediterranean sun, sea and sky.
Matisse seems to have painted Derain with full sunlight striking his face and casting a heavy shadow down the right cheek. In addition to the sunlight Matisse has brought in two other predominant colours of the scene, blue and green. What has then taken place is a process of adjustment to produce an effect of maximum intensity recreating what Matisse called his 'sensation'. But the effect must also, of course, be balanced and harmonious. In his A Painter's Notes published in La Grande Revue in 1908 Matisse wrote: 'If upon a white canvas I set down some sensations of blue, of green, of red ... it is necessary that the various marks I use be balanced so that they do not destroy each other ... From the relationships I have found in all the tones, there must result a living harmony of colours, a harmony analogous to that of a musical composition'.
This is interesting not least for its restatement of the aim of a musical aesthetic for painting. Matisse's 'living harmony' is based on Seurat's discovery of the dynamic but balanced relationship between complementary colours, and in the portrait of Derain all the adjustments that Matisse has made to perceived reality have been in order to create complementary combinations. The sunlit orange-yellow side of the face is against the blue part of the background. Against the green area Matisse has adjusted the colour of Derain's beret up to a strong red and to complement that on the other side has, entirely arbitrarily, rendered the hair as green. For consistency in his colour scheme, he has gone on to give Derain green eyes and a green moustache as well. The shadow is green where Matisse has assumed reflected colour from the background, but in the twilight zone between the shadow and the full light the true colour of the shadow, blue, appears, and on the cheekbone it is placed against a broad stroke of complementary orange. The discovery that shadows are coloured and that they are the complementary colour of the light that casts them (orange or yellow sunlight blue or mauve shadow) was of great importance to the Impressionists, Post-Impressionists and Fauves in their development of an art of pure colour.
Simon Wilson, Tate Gallery: An Illustrated Companion, Tate Gallery, London, revised edition 1991, p.116