This is the be-all and end-all, the beginning and the end of the whole matter, and here therefore follow a few hints with regard to it.
And there is one rule of such dominating importance that all other hints group themselves round it; and yet, strangely enough, I cannot remember seeing it anywhere written down.
Take three tints of glass—a purple, let us say, a crimson, and a green.
Let it be supposed that, for some reason, you desire that this should form a scheme of colour for a window, or part of a window, with, of course, in addition, pure white, and probably some tints more neutral, greenish-whites and olives or greys, for background.
You choose your purple (and, by-the-bye, almost the only way to get a satisfactory one, except by a happy accident now and then, is to double gold-pink with blue; this is the only way to get a purple that will vibrate, palpitating against the eye like the petal of a pansy in the sun). Well, you get your purple, and you get
your green—not a sage-green, or an "art-green," but a cold, sharp green, like a leaf of parsley, an aquamarine, the tree in the "Eve" window at Fairford, grass in an orchard about sunset, or a railway-signal lamp at night.
Your crimson like a peony, your white like white silk; and now you are started.
You put slabs of these—equal-sized samples, we will suppose—side by side, and see "if they will do."
And they don't "do" at all.
Take away the red.