My choice of colors does not rest on any scientific theory; it is based on observation, on feeling, on the very nature of each experience. I.. ..merely try to find a color that will fit my sensation. There is an impelling proportion of tones that can induce me to change the shape of a figure or to transform my composition. Until I have achieved this proportion in all the parts of the composition I strive towards it and keep on working. Then a moment comes when every part has found its definite relationship, and from then on it would be impossible for me to add a stroke to my picture without having to paint it all over again.
— HENRI MATISSE