In order to understand the nature of colour it is important to realise that we cannot actually see a beam of light. When we look into outer space we see millions of stars. Since all these stars spread their light to all directions we can reasonably assume that space is filled with huge amounts of light. Still, when we look up, we can clearly see that the space between the stars is black. We can only see the sources of light: the stars, not the light itself. And only then when we really ‘look at it’.


Let us concentrate for a second on the difference in perception of a lamp and a radio in a house. We can hear a loud radio anywhere in the house, it doesn't matter much whether or not we turn our ears to it. The picture shows how sound travels around a ball towards the ear. The sound doesn’t carry much information about the form of location of the balls. Sound only gives a very limited sensation of form, and thus a limited sensation of space.


This picture shows a lamp. The blue ball is an obstacle for the light of the lamp. As a result of the presence of the ball, the lamp is not directly visible. We can only see the light of the lamp indirectly, reflected by the green ball. Now a striking, almost magical phenomenon becomes apparent: as a result of the light meeting the balls the green ball has become visible, it got colour. So where light touches an object, colour is created.
From the fact that the green ball is visible, but not the lamp, the onlooker can gather that the lamp must be hidden behind an unknown object: the blue ball. Lamp, balls and onlooker have a fixed relationship and together they create a sensation of form and space. One of the most important features of this sensation is colour.