Most Helpful Guy
Too much or too often is a red flag. "I'm not confident in how I look so I dump chemicals in my hair to look different every so often. I've met many many women and only a handful of them having a dying schedule and are confident in their appearance and aren't attention whores. However, dont blame this on guys. Its women who slut shame other women. Most guys are too busy trying to get a peek at the goods to give a shit about anything else. If you want to do it, do it and who cares about any other opinion. Don't do it too much though, its hard on your hair and you'll look like a chemo patient in your mid thirties.
Most Helpful Girl
From what i've gathered: If you're confident enough to pull it off you're going to get more positive feedback than negative. Not saying your friend isn't, some guys are just rude. My guy friends all think colored hair is cool