He's nervous about Cade being right there. This could be getting into provoking territory, but he doesn't see anger in the paleness. Anders will stay aware, but for now, at least, he thinks he's not behaving too riskily.

Anders' own expression turns very, very smug as he's looked over. "What, intimidated by another man being pretty? Or are you embarrassed? You don't have to be either. My ass is rather fantastic; it's simply a fact. Did you want to turn around for an assessment of yours?" The answer is likely to be no, and Anders is more than ready to be amused by that.