Colour Measurement and Mixture

by Sir William de Wiveleslie Abney

(2)	{
		Red	4
		Green	35
		Violet	25

Deducting one from the other we get as the complementary colour,

(3)	{
		Red	125
		Green	25
		Violet	75

This is a complementary colour, but like the green itself it is mixed with white light; but we can easily deduce what is the simplest complementary colour; for we have only to deduct the possible white light from the second measure. Now evidently the greatest amount of white light is when the whole of the green is taken as forming part of it, with the proper proportions of red and violet, and these we can obtain by taking the proportions of the colours in (1); therefore deduct—

(4)	{
		Red	69
		Green	25
		Violet	41.5

and this would leave as the complementary colour without any admixture of white—

(5)	{
		Red	56
		Violet	33.5

which is a purple as would be expected.

Now to give the same dilution of white to the complementary that the emerald green has, we must take away from the emerald green all the white mixed with it, and add that quantity to the complementary. The white in the emerald green can be found by treating the whole of the red as going to form the white; we then have from (1)—

(6)	{
		Red	40
		Green	14.4
		Violet	24