Thanks for the info. It even has a paint code which I never knew about. I took the tail lights out and could see that whoever painted it did not remove them, instead just masked them, so there is a different shade which was hidden. It does not look like the silver argent paint I bought to touch up the grill (I think it was from Herb, but can't remember exactly) which was more sparkly with bigger looking flakes. It is light but dull, not sparkly.
Research tells me there is no perfect substitute for the original but I find a lot of opinions and discussions on what comes close (including a DIY mix). I've seen the Krylon dull aluminum mentioned as a pretty good match so I'm going to give that a test.