Hi Bruce,
I know what you're talking about, I have the same issue on my aluminum radar arch and I in fact used the Johnson ob paint in a can. To be honest with ya, its way on top out of the way and no one can see it. I also took a large chip of my original paint and sprayed a littl epaint and guess what, it was extremely close! I think even if you get the original paint, it wont match perfectly either due to age and sun bleach, dirt etc. The main thing is to get it painted on so the corrosion doesnt eat on the aluminum.
Ski