With light brown hair, you probably could get away with either Pimpin' Purple or Deep Purple and possibly Wildflower, which I've heard is somewhat of a lighter version of Deep Purple. It tends to look a little bit blue in the pictures I've seen of it.
I've used Deep Purple and initially it looks almost black. Unfortuanately, if you hair is in good condition, the color won't stay too long. The darker stuff lasts longer, but be prepared to redo it pretty often. I used DP on my husband last year and the color faded out before the staining on his scalp went away, but he has really dark hair (nearly black).
Good luck.