dj's suggestion of using fabric is excellent. When I read it I looked over my shoulder to my wife.... "honey... can I borrow some of your fabrice paint?"
Let me tell you, it worked great. One thing I found when applying it was that once I got some paint on the tip of the tool I was using, the first and maybe 2nd rivit were too big, the subsequent two or three were just right, and then too small. So what I did was dip the tool in the fabric paint, attempt a couple of rivits on some scrap material, then quickly go to my subject and do a cuple, then start the process over. As was said earlier if you don't like it, clean it off real quick. Great tip dj, thanks much!