Most Helpful Guy
Stars are how high a question is ranked, 1 if it's dumb and annoying, 5 if it's wicked awesome and thought provoking, or 2-4, which nobody ever uses. Basically, if a question is ranked with stars a day after it's made the QA gets a little extra Xper (equal to the Star level, so long as it's more than 1 star).
Up arrows and down arrows depend on whether you agree with an answer or find it offensive. If you agree with it, vote it up, the answerer gets an Xper point for it and the total goes up by one. Same thing for down arrows, if you find it to offend the very fiber of your personality, vote it down, but it doesn't have any practical purpose.
Blue is for boys, pink is for girls. And level rankings each have colors, but those don't matter too much.