Two colour pigment fields, one red and one white, are positioned in close proximity on the floor. First white light is shined on both of them. After some time the light on the white pigment is changed to red. At the moment when the white pigment is illuminated with red light, the perceived colour matches that of the red pigment bathed in white light. Without knowledge of the lighting conditions, both fields seem to contain red pigment. Thus both fields appear to have the same colour, though the origins of the colour are distinct.
Lights of different colours pass over the pigment carpet one after another. A narrow strip on the outer edge of the white pigment surface serves as reference to indicate the colour of the projected light.
For example, the colour yellow is produced by superimposing red light with green light on the white field. This additive colour combination makes the colour combination lighter. On the field with red pigment, the white light is slowly replaced by green light. This causes the red pigment to assume a brownish tinge (ill. 7). This is a result of a subtractive colour combination of green light and red pigment, which makes the colour appear darker.
The effect of cyan-coloured light is especially dramatic. White is created from an additive mixture of red and cyan, while as a result of a subtractive mixture the red pigment appears dark grey when combined with cyan.