I think it is cool if it is something you want to do for yourself. I'm not so sure about the whole 'all I wanna do is be different' thing though. It tends to come across as distasteful when the things you do don't match who you actually are.
Personally, wearing 'hip' clothing and trying to fit in with my, then, friends, was the worst thing I could've done. Now, I wear things that are different, but not because I want to be different, I wear the things I like, things that suit my personality. Now, I can't stop you from having colourful hair. All I'm saying is, think about why you're doing what you're doing and if it really suits you.