From Maholy Nagy Vision in Motion 1956, pp 154 – 176
Although the spectrum consists of an infinite range of wavelengths, we resolve them into six to ten primary colours, following the psychological law of the threshold of optimum discrimination.(p.159)
[W]hile innumerale gradations of colour exist, we tend to react to simple but strong sensations, and often we simplify what we see to prevent its throwing us into confusion. The old painters generally worked with two complimentary pairs, red-green, blue-yellow.
It was known already to Aristotle [in "De Sensu et Sensilius"] that colours in juxtaposition will mix on the retina when seen from a distance.
Over the centuries painters accumulated secret methods to chieve the radiance of colour oserved in nature, by subtle manipulations, through fine shading, underpainting, transparent varnishing, juxtaposition of complimentaries, psychological after-images, coloured spots, shadows and other finesses of a colour dictionary.
Through such efforts they often achieved an intensity almost equal to the natural phenomenon. The most successful aplications resulted when the painter did not mix the pigments on the palette, but “in” the eyes of the spectator.
Nevertheless the real fascination of colour, the inner glow of a painting – its foremost quality – could never be put down in rules. This depended on the stroke of genius and had to be found and interpreted anew by every painter.
For [the prerenaissance painter] colours became active by combining them solely in relation to each other.
Though cubism in its first phase did not work with strong primary colours, the introduction of numerous whites and greys and browns created a new colour consciousness, new degrees of spatial refinement in the receding and advancing values. Kandinsky and other abstract painters such as Malevitch, Mondrian and the constructivists developed this further by plunging into the clear primary colours. This advance was bound to be followed by the direct use of light itself, pleading for a higher order of space articulation…
Until Seurat, painting was mainly the prolem of using colour to produce the illusion of volume in space. Seurat, possessed by the idea of vibrating light, employed colour as an element of light symphonies. The shapes in his paintings were without detail and were used only as the carriers of a coloured light structure. In this sense, Seurat is the great progenitor of the contemporary painter who brings a refinement to colour relationships through visual devices which produce elemental impacts.
Contemporary painting [emphasises] the direct sensuous perceptional impact of colour on the spectator.