familiar experiment of fixating for some moments a colored
object, say red, and then transferring the gaze to a white or
gray expanse. The image of the object appears thereon in the
complementary green. Per contra, the most complete lack of
contrast makes the most unpleasing combination, because instead
of a refreshing alternation of processes in the retina, a
fatiguing repetition results. Red and orange (red-yellow), or
red and purple (red-blue), successively stimulate the red-
process with most evil effect.

This contrast theory should, however, not be interpreted too
narrowly. There are pairs of so-called complementaries which
make a very crude, harsh, even painful impression. The theory
is happily supplemented by showing<1> that the ideal combination
involves all three contrast factors, hue, saturation, and
brightness. Contrast of saturation or brightness within the
same hue is also pleasant. For any two qualities of the color
circle, in fact, there can be found degrees of saturation and
brightness in which they will form an agreeable combination,
and this pleasing effect will be based on some form of contrast.
But the absolute and relative extension and the space-form of
the components have also a great influence on the pleasurableness
of combinations.

<1> A. Kirschmann, "Die psychol.-aesthet. Bedeutung des Licht
und Farbencontrastes," _Philos. Studien_, vol. vii.

Further rules can hardly be given; but the results of various
observers<1> seem to show that the best combinations lie, as
already said, among the complementaries, or among those pairs