I let DS pick his clothes every day. Shorts and a jumper with long socks - fine. That's FiL's fashion choice too. Sometimes I'll ask him to put on a shirt, but he picks what he likes.

I buy the clothes (DS picks and I can veto sometimes) and remove them when they need it, so it isn't like he's going out dressed that badly. Just cos I wouldn't wear rust-orange and bright red together doesn't mean DS can't.