In the nineteenth century there were a number of color terms to describe moods/thought processes - naturally now that i'm writing about it the only one I can remember is a "brown study," which is a sort of gloomy reverie - and many of them seem so vivid and useful to me that I always find it sad that they've fallen out of fashion.

Oh, and I can think of two color terms for cowardice: being yellow, or showing the white feather - although I've also seen white used as a synonym for honest, brave, true, all the Boy Scout virtues (in a book about Boy Scouts, actually). (There's probably a racial subtext to that meaning, although I haven't chased down the etymology or anything.)

"Blue devils" - and the green-eyed monster, which is still somewhat in use - both portray emotions as something that come from outside to attack us, which maybe doesn't mesh with a modern (post-Freudian) popular understanding of psychology where emotions well up from within us. Or something. I need to give this more thought.