I'd go with the color you don't already have, or whatever will fit with your wardrobe best. As NWGal said, though, considering color transfer, the black will be less maintenance.
I love the Aurora and pewter that just came out. I currently have the chalk color block one that I am waiting to start using in the spring. I'm currently still wearing all my black purses because that's the kind of mood I'm in right now. If only I could find a job. Then I'd totally treat myself to a new Cassie.
Also, if I didn't already have the chalk/taupe color block, I would get the all taupe leather one. I know there was one available this past fall that was half leather and half suede. Looks like they've gone ahead and made it all leather.