*looks* Yep! I think you should try it. But, bleach out whatever you're going to dye blue before you put it on. Odd colors like that don't go over natural colors easy unless they're very light.
Well, depends on what you like. It'll stay in longer if you do all of your hair because you can put a little bit of dye in your shampoo and when you wash your hair it'll keep it from getting lighter faster.