It wasn’t the fact that it looked good on him that he got crap for, it was the question whether it was appropriate for the occasion (a press conference discussing the potential escalation of military strikes in Syria).
Tradition demands that you wear a dark suit for something as serious as discussing the sacrifice of other people’s lives. A tan suit has more of a lighthearted vibe and is therefore something you’d wear to a festivity, not when discussing drone strikes.