I responded back to Delta and asked for some sort of paint codes. They just told me that no paint codes were transferred during any of the sales and that the best way to get a match was to take a sample and get it matched. Oh, well. I tried.
It looks like the Rustoleum Smoke Gray will be fine, unless and until I can look under a tag and see if the original color is still there.
On a related side-note, I called Kurt and asked about paint colors on their vises. They must get that a lot because they told me that Ford Blue was a rattle-can match. I guess I'm surprised that Delta doesn't have something similar.