Rihanna and her green nails are just a little bit late for St. Patrick's Day , but that's all right. The star got up close and personal with her young fans after performing a benefit concert  last night at a Chicago club. You voted that you (overwhelmingly) liked her black nail polish over any of the other wild and crazy colors  that she's worn recently, and now you've got another shade to choose from. That Rihanna sure does love unusual polish. Do you?