Neurology Center

Depression is black. That's been the view of Western culture ever since the ancient Greeks, with their concept of "melan cholia" (μελαγχολία) - black bile. The idea was that psychological states were associated with particular bodily fluids; melancholy was associated with the "black bile" of the spleen, as opposed to the go-getting, passionate "yellow bile" of the gall-bladder

What this "black bile" (melan chole) actually was is rather mysterious. The gall bladder does indeed produce bile, a digestive juice which is greenish-yellow, but the spleen doesn't secrete anything as such. It itself is a dark greyish-purple, which might have given rise to the idea that it contained something black. Here's another theory.

The other color associated with depression is blue, of course, as in The Blues. However, when picturing depression-blue, I think most people generally see it as something rather close to black. It's the sky at twilight, not a bright summer's day, right? It's not a happy blue.

Winston Churchill famously referred to his depression as his Black Dog. There's a rather nice correspondence here with Chinese, though I doubt Churchill knew it. Here's the Chinese character for black and (one of) the characters for dog:
Write these as two separate characters and it says, well, black dog (badly). But there's another character which consists of "black" & " dog" combined:

This means silence; quiet; speechless; mute.

This is as good a one-word description of depression as any. Churchill's metaphor has always struck me as slightly misleading in one sense (although it's excellent in others): depression is not a thing; not even a black one. It is a lack, of motivation, energy, joy, imagination; you don't wake up and feel depressed, you wake up depressed and feel terrible, but the depression is hidden, only evident in retrospect, just as you don't tend to notice how quiet it is until a noise breaks the silence.