All I can think of is doing a google search for skin bleach. I'm not sure they sell it in stores, but if it were me, I would rather buy it online than in a store anyway to save on embaressment
another trick you can do, is drink light colored soda. I hear darker soda, such as colas and what not, can have something to do with the color "in that area". So Sprites and 7ups are what you should drink instead if you drink soda. Or just drink lots of water
I hope that helps and/or you find something that does.