Contrast = dissonance, and hence a maximum expressive effect. I will take as an example a commonplace subject: the visual effect of curled and round puffs of smoke rising between houses. You want to convey their plastic value.. Here you have the best example on which to apply research into multiplicative intensities. Concentrate your curves with the greatest possible variety without breaking up their mass; frame them by means of the hard, dry relationship of the surfaces of the houses, dead surfaces that will acquire movement by being colored in contrast to the central mass and being opposed by live forms; you will obtain a maximum effect.

in 'Functions of Painting by Fernand Leger'; p. 14 - Contemporary Achievements in Painting, Fernand Leger (1914)