I always take ZMA before bed, so I'm not sure how it effects my urine color. If my pee is neon green first thing in the morning, well that's normal.
I'm no expert, but I don't think there's any particular reason why you can't take ZMA at the age of 17. Although you're so full of test right now it might not even be neccessary.
(It's worth it just for the freaky dreams, though
)