Here's what I was able to come up with from the ZR-1 Net:
"Go to your local hobby store the one that sells plastic models, and get a paint that is made by Tamiya. Its called Tamiya color, Acrylic Paint and the code number is X-11 (chrome silver). Don't worry about the color (chrome sliver) when it dries its the exact same color as the wheel. Just remember to stir the paint and do not shake it.
Touch up the ding with a small soft brush filling the ding to just higher than the surface of the surrounding paint. Let dry for 24hrs then lightly buff down with some polishing compound to the same surface level of the rest of the paint. Be sure that the wheel is cool before attempting to touch it up.
Thanks to Pete Bordonali for this info.
Another member has found Testors #1181 Aluminum FLAT ENAMEL in the little tiny bottle (like kids and dads use for model airplane building). It is very close and looks great. And it's cheap - $1.10 at Michaels craft stores. It makes the outside wheel weights almost disappear too."
Todd cerami