Color is crucial in painting, but it is very hard to talk about. There is almost nothing you can say that holds up as a generalization, because it depends on too many factors: size, modulation, the rest of the field, a certain consistency that color has with forms, and the statement you're trying to make.
So many of man's actions appear to have no immediate consequence but, concealed, do their work until finally all catches up and forms a complex web of cause and effect.