In 18th century London, Sir Joshua Reynolds explained to students that the color blue need not occupy the foreground of their paintings. Instead, it should be constrained to the background:
“It ought, in my opinion, to be indispensably observed, that the masses of light in a picture be always of a warm, mellow colour, yellow, red, or a yellowish white, and that the blue, the grey, or the green colours be kept almost entirely out of these masses, and be used only to support or set off these warm colours; and for this purpose, a small proportion of cold colour will be sufficient.”
Thomas Gainsborough addressed these remarks by painting his famed portrait of The Blue Boy.