the law connecting the corresponding colours shows, as may be seen in
the following diagram. Here, red, yellow and blue as three primary
colours confront the three remaining colours, green, violet and orange
in such a way that each of the latter represents a mixture of the two
other primary colours. (Fig. 10.)

Colour and contrast-colour are actually so related that to whatever
colour the eye is exposed it produces a counter-colour so as to have
the sum-total of all the three primary colours in itself. And so, in
consequence of the interplay of outer and inner light in the eye, there
is always present in it the totality of all the colours.

It follows that the appearance of the contrast-colour in the field of
vision is not, as the Newtonian theory asserts, the result of fatigue,
but of an intensified activity of the eye, which continues even after
the colour impression which gave rise to it has ceased. What is seen on
the neutral surface (it will be shown later why we studiously avoid
speaking of 'white light') is no outwardly existing colour at all. It
is the activity of the eye itself, working in a dreamlike way from its
blood-vessel system, and coming to our consciousness by this means.

Here again, just as in the simple opposition of light and dark, the
perception of coloured after-images is connected with a breaking-down
process in the nerve region of the eye, and a corresponding building-up
activity coming from the blood. Only in this case the eye is not
affected by simple light, but by light of a definite colouring. The
specific destructive process caused by this light is answered with a
specific building-up process by the blood. Under certain conditions we
can become dreamily aware of this process which normally does not enter
our consciousness. In such a case we see the contrasting colour as