You can change the colour range in user settings (somewhere near the bottom), furthermore, you could use the CSS generated from it as a starting point to completely redefine the display styles, any way you want.

I'd like to take the opporunity to make a public call for people to submit their favourite edited CSS styles — though I'm not exactly sure where. We've been thinking along the lines of providing presets of styles, just like the general themes for the whole site — and yours might be in it.