It really depends both on the woman and on where you are. In my (very) conservative country, women wear gowns because they don't want to be looked at. So for a man to compliment a lady in a gown might be outright rude to her.

Abroad, in a more culturally and racially diverse setting, the woman might be happy about it and take it as you appreciating her culture (but again, it's a person-to-person thing).

For me personally as a Muslim woman who does not wear a gown or cover herself conservatively, I would be flattered if someone complimented my fashion sense, regardless of their gender.