Plant colours are light colours. They come into being through the living power of sunlight. Not a green leaf, purple hollyhock or yellow buttercup could shine out so colourfully as it does if it were not for the action of the sun. This distinguishes plant colours from earth colours, mineral colours and synthetic colours which, having been stored underground in the form of metals or mineral oil, represent the earth forces. Each plant has its own individual light aura, which the plant colour production process brings out in a unique coloured light.

Earth colours and synthetic colours make a dense impression. Plant colours on the other hand are full of light and movement, and have something extraordinarily vital about them. This is what gives them their special artistic expressiveness, and explains why they are so valuable in painting therapy.