Yup, they look like normal, white golf balls, but lo and behold, these HenkaQ balls actually change colors when they're exposed to sunlight. The surface of each ball is treated with a photochromic compound like the kind used on those gay sunglasses (and I mean that in the 8th-grade sense, of course) that get darker to protect your eyes from UV rays. The balls promise to turn one of four colors—light blue, blue, yellow or purple. The website is in Japanese, so I'm not sure if you can choose the actual color, but it still sounds good to me. Keep in mind, though, I'm not an avid golfer, so maybe colored balls don't quite have the same appeal...? Also check out the fluorescent ball for any night golfing you may have in mind.
Colorful golf balls [Odd Japan]