No, it doesn't mean he's gay.
Albeit, some people choose purposely gender biased colors to hint at something.
but I've settled on a happier and more insightful reason people have favorite colors- I read in an article that our favorite colors denote the persona of ourselves. I'm green, so I'm lively and quick witted- and pink I believe is supposed to be excited, lively, mild mannered and sweet? I hope that's right, because my BF likes pink too...
(and has his ears pierced...??)