On a classic-styled steel frame, definitely silver IMO. I like black cranks (both my carbon fiber bikes have black CF cranks) but the aesthetic doesn't work as well for me on a skinny tubed frame. To be really honest, I don't like the look of the new Shimano cranks in general on a skinny tubed frame. Stronglight and TA both make some good looking cranksets if you don't mind the slight mismatch of components.