Blue is always different from yellow, for example: depressed (the blues), where yellow is gay, loyal (true-blue), where yellow is cowardly, and the like. Blue has a similar meaning to yellow about once in a blue moon.

—Marshall Sahlins, quoted by John Gage in the essay Colour and Culture, from Colour: Art & Science edited by Trevor Lamb and Janine Bourriau, 1995.