In my opinion, it sort of depends on what color your hair is, and what would look best with it.

Hope this helps!

~elementgirl 

I would say purple.

Okay, first of all, go you! Dying your hair, even a streak, is something brilliant because it shows you are unique. I love the idea, and you should totally do it. As for social reasons, unless you want to be ordinary - and trust me, no one wants to be ordinary - don't care what people think, do what fits you and what represents you.

As for the color, it really depends on what you like the best, and what hair you have! I love both colors, and since they are so similar shades, I don't think it would matter which one you got. Just go with your heart!

And have fun showing off the new style, AutumnArtist! I think it is a spectacular idea. 

I like both of those colors also!  I don't think you should care what people think, even though sometimes thats hard to do.  You should do what you want your hair to be like.  After all you're the one wearing your hair, so it should be how you want it!  If you are still having trouble choosing, you could dye one streak blue not permanently.  Then, you can try purple (not permanently).  There is dye that goes away after a while.  When you're done with both colors, you can decide which one you like better. 

Blue and purple are both great colors, and would both go great with brown curly hair! It's really up to you, but if you can't decide, maybe try a blueish-purple, or even a little of both! Hope this helps!