I would think this would be very sarcastic to say to someone. In reality what a person is really doing is giving the individual a dig.

I would chalk this up to pure ignorance and lack of social skills.  Personally, I don't mention someone's hair or any other change in appearance unless I really like it.  If I think it was a bad idea then I keep my mouth shut.  However, I always consider it open season when watching someone on TV and you can often hear me exclaiming - WHAT was he/she thinking?!!!

yes this could be rude or ask them if they intended for their hair to look like that. and be sure to have a yuk look on your face.

Couldn't you tell by their expression?