You really cant go wrong with any color. IF you like class and see the TSX as a 'classy' car I would suggest black. Silver is decent as well but there are many silver cars out there and it would not stand out as much.
When I was deciding, carbon grey and silver were my top choices. Silver won out and I LOVE it. Definitely get the 6speed if you want to maximize the fun level, but get whatever suits your tastes....meaning go test them both out, and then decide.