It's good if done right, but possibly a disaster if not, like anything. It could work if it's a carefree girl that is almost making a social commentary out of it. I think people are so hell bent on liking "real" things that they don't care if it's done through fake means, but once someone points out that it's fake out in the open, it's magically unwanted. People are basically stupid animals and I would respect a girl that could carry crazy hair color, and I might even find it aesthetically pleasing.
I have no issues.. the problem is that some how it could give the feeling that they are a bit crazy and irresponsible.. but I am sure it is a steryotype... I am open minded to anything as long as she is sensible and loyal