Categories - Custom Background Colours (To Each ID)?

[Inked_Mono]

Does anybody know of a way to set custom background colors for your categories? As it stands, they're all defined as a blue;

http://i.imgur.com/mySBJJg.png

As you can see with "Off-Topic Discussion" and "Additional Forums", but is there a way I'd be able to set a unique color for each of those categories? I've tried looking around, but can't seem to find a way to.

Thanks in advance!