I have a custom theme that's pretty minimal, because I find lots of colors distracting. Colors are vaguely based it on pen on paper: white: background dark blue: foreground light gray: brackets and commas and stuff red: literals (strings, numbers, true/false) black: comments This means comments and literals stand out, which are usually the things I don't want to miss when I'm reading through code.
(but yes I make my comments gray)