Cox, David: A series of progressive lessons intended to elucidate the art of painting: with introductory illustrations on perspective and drawing with pencil (London, 1845)

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water to the tone required; it is denominated simple, because mixture is not
necessary to obtain it. A compound tint is produced by the mixture of
colours, as red and blue to produce a purple; blue and yellow to produce a
green ; red and yellow to produce an orange, &c. ; these are also called
derivatives, because they have no existence but by mixture. All colours, or
rather tints, when used simply, are clearer than when compounded; and they
appear to greater advantage, whatever the strength, by being judiciously
opposed to compound tints. Thus red, in its varieties of tint, may be
contrasted by green in its varieties; blue, by orange; and yellow, by purple
in its varieties.
It will be observed, that red, blue, and yellow, the primitive or simple tints,
do not afford the most pleasing contrasts; nor do the derivative, or compound
tints, orange, purple, and green, as opposed to each other; hence may be
deduced a direction in the choice of tints to produce the most agreeable
contrasts; and it is also worthy of notice, that such selections, with respect to
contrast, produce a perfect harmony every way consistent with the laws of