I found this isn't always true...it can vary based on the way your frame was painted. I discovered this while looking for touch-up paint for my Interloc. I contacted the company and they no longer had any and couldn't give me any sort of paint code. I called a local auto paint store and they said I could bring it in and they could help me try to match it. As soon as I walked in the door, the guy said "Oh...that's gonna be tough". He said my frame had been shot with two different colors...a silver undercoat and then a close-to-royal-blue metallic top coat. So for touch-up, there was really no way to get the silver undercoat without great attention to detail and tons of time. So we got as close as we could with a standard paint, he added a few things to it and I brought it home. It's too dark but I reached the point where the time invested for touch-up became not worth it.

If I had to do it all over again...nail polish.