I hadn't really paid much attention to the webbing color with the chrome alligator skin texture buckles, but thinking back, I don't ever recall seeing an original set in a car with anything other than black webbing. Seen a lot of restored cars with color-keyed webbing though... including pace cars with blue. On the pace car I restored, the original belts were black webbing. I know on at least one other restored pace car, I inquired with the owner on the webbing color and they said that they thought they remembered it being black, but thought it should be blue...
Guess this is something we ought to discuss in another topic.