The Story of Art, E.H. Gombrich Page 154, Zettel 148

The great artists of subsequent periods had made one discovery after another which allowed them to conjure up a convincing picture of the visible world, but none of them had seriously challenged the conviction that each object in nature has its definite fixed form and colour which must be easily recognizable in a painting. It may be said, therefore, that Manet and his followers brought about a revolution in the rendering of colours which is almost comparable with the revolution in the representation of forms brought about by the Greeks. They discovered that, if we look at nature in the open, we do not see individual objects each with its own colour but rather a bright medley of tints which blend in our eye or really in our mind. - The Story of Art, E.H. Gombrich Page 154, Zettel 148