First, here are some celebrities with normal shaded hair colors:
I've noticed that one of the big trends right now is to do ombre hair with un-natural colors; especially blue. If you want a drastic change blue is definitely the way to go. Pink is also a great color for end highlights because it looks soft and feminine. If you have darker hair, get your ends stripped of your original color before putting on a new color. This way the new color appears stronger and isn't affected by your original color.