Isaac Milner's theory of colours and shadows 3

11. This last observation shews us, that white may be considered as made up even of two colours only, and we shall find it very convenient in the explanation of the phenomena in question, to consider white as so made up, namely, of red and green, of yellow and purple, or of blue and orange. These colours are called contrasts to each other respectively: their apparent brilliancy, when they are placed contiguous to each other, is promoted in a remarkable manner, but they cannot be mixed together without mutual destruction to their natural properties, and an approach to a white or a grey colour.