GENERAL CONSIDERATIONS.
1. Regarded from an art point of view, there are but three colours—i.e., blue, red, and yellow.
2. Blue, red, and yellow have been termed primary colours; they cannot be formed by the admixture of any other colours.
3. All colours, other than blue, red, and yellow, result from the admixture of the primary colours.
4. By the admixture of blue and red, purple is formed; by the admixture of red and yellow, orange is formed; and by the admixture of yellow and blue, green is formed.
5. Colours resulting from the admixture of two primary colours are termed secondary: hence purple, orange, and green are secondary colours.
6. By the admixture of two secondary colours a tertiary colour is formed: thus, purple and orange produce russet (the red tertiary); orange and green produce citrine (the yellow tertiary); and green and purple, olive (the blue tertiary); russet, citrine, and olive are the three tertiary colours.