I dyed the tips of my hair a rather nice purple color once, and being a blond, they really stood out. However, I did get quite a few comments on people asking me how long it took my roots to grow out, seeing as they thought I had dyed my entire hair and that was just the leftover.
Eventually I just dyed my entire head that purple color to stop the comments and I loved it. Just keep in mind every color will eventually fade out, so you will have to keep dying it. If I can offer a tip? Use shampoo for color treated hair, as well as a conditioner to keep the color longer. This will also help keep your hair healthy, since the ammonia in the dyes will strip your hair of most of its natural oils and will eventually damage your hair if you dye it too often.
Dyes with less ammonia will harm your hair less, but the color also wont last as long.
Hair is one of those wonderful things that will keep growing back no matter what you do to it, so you may as well have fun!