On mine it's the one coming off the red terminal on the tweet itself. I would guess the red stripe per normal convention. As long as you keep it the same left and right, it won't matter. If it sounds wrong, swap them on both sides.
I'm thinkin it's the red stripe one too. I know on some of my speakers the negative is the one with a black stripe, and since black=negative and red=positive, I'd try that.