"Colors ... are never seen in isolation; they are so puzzlingly variable as to justify a curious observation made by Goethe while he was concerned with the theory of color:
'The chromatic has a strange duplicity and, if I may be permitted such language among ourselves: a kind of double hermaphroditism, a strange claiming, connecting, mingling, neutralizing, nullifying, etc., and furthermore a demand on physiological, pathological, and aesthetical effects, which remains frightening in spite of longstanding acquaintance. And yet, it is always so substantial, so material that one does not know what to think of it.'
"The elusiveness is not so much a particularity of perception as it is of cognition in general. The privilege of observing everything in relation raises understanding to higher levels of complexity and validity, but it exposes the observer at the same time to the infinity of possible connections. It charges him with the task of distinguishing the pertinent relations from the impertinent ones and warily watching the effect things have upon each other."
-- Rudolf Arnheim, Visual Thinking (Berkeley CA: University of California Press, 1969).