As long as it's not black nail polish. I don't like black nail polish anymore. Many guys paint just one fingernail...if you paint all of them...then it will look too much like a girl, maybe...unless that is what he is aiming for. :p
You shouldn't ask opinionated questions on here because then you are going to get hurt by other peoples opinions. If you want to, go right ahead. You should not care about others opinions on things you doubt your own answers to.