These Bleulab Reversible Detour Leggings in Granite are so cute,they are grey on one side and black on the other. Celebs like Giuliana Rancic and Kourtney Kardashian are both fans of them.
You can get them at Singer22.com. 

You can also get them in a different color.These are Coated Plum on one side and French Chalk on the other.