Blue, as in DEPRESSED.
The Big Bang Theory Season 4, Episode 22
...green is jealous
and blue is DEPRESSED.
The Big Bang Theory Season 4, Episode 22
...because I'm fun,
I'm not clinically DEPRESSED at all.
The Big Bang Theory Season 6, Episode 5
Has he been DEPRESSED?
Breaking Bad Season 2, Episode 2
He's DEPRESSED because he's pathetic
and creepy and can't get girls.
The Big Bang Theory Season 2, Episode 12