I've heard "You look gay." I've heard "You don't look gay." Never before have I heard "You look bisexual." It happened in my graphic arts class and it went like this: David [guy on my left]: "Hey, Alex [girl on my right], are you bi?" Alex: "No. Well, I don't think so. I guess I could be. Why?" David: "You just look bisexual." Yeah so.
For some reason I have this weird belief that all bisexual people are attractive-looking, so there's that. Maybe they're complimenting you
Maybe "you look gay" sounded a bit offending to the guy saying it, so he tried to improve his remark by lowering the "gay" word by a few levels on the kinsey scale!