I'll join the chorus: black chain rings are the business. Black cranks are... somewhat problematic.
OK, sure: If you're talking about a modern CF alien-vs-predator looking thing, with the all-black 4-arm 105 stuff that everyone says is so wonderful, and billboard sized logos on the super fat carbon frame, then great.
But on a vintage bike, I don't think I've ever seen a black crank that wouldn't look better in silver. EDIT: Although, now that I think of it, I've seen a few vintage builds that make use of of black crank and silver rings that look pretty sweet.
Northbend posted one up here a day or two ago.
My silver+black contribution: