I remember being told by a painter of his placing a red sunset landscape upon the flat roof of a studio building to dry, and on going to it a few hours afterward he found the surface of it so warm to the touch--so sensibly warmer than the gray and blue and green pictures around it--that he brought a thermometer to test it, and found it had acquired and retained heat.

It was actually warmer by degrees than the gray and blue pictures in the same sun exposure.
We instinctively wear warm colours in winter and dispense with them in summer, and this simple fact may explain the art which allots what we call warm colour to rooms without sun.

When we say warm colours, we mean yellows, reds with all their gradations, gold or sun browns, and dark browns and black.

When we say cool colours--whites, blues, grays, and cold greens--for greens may be warm or cold, according to their composition or intensity.

A water-green is a cold colour, so is a pure emerald green, so also a blue-green; while an olive, or a gold-green comes into the category of warm colours.