Now I am very interested in the reply to this question.
I have an '82 GL 500i that used to be silver but the tank, sidecovers and fenders were resprayed a custom-mixed bluish silver-grey by my good friend Norman Johnson about 15 years ago.
We painted the fairing black and the bags as well as the trunk.
What I was going for at the time was a black and silver sort of look but the mixed paint turned-out rather bluish.
It didn't look bad and I rode it over 100,000 miles that way but recently I've been thinking about returning the tank, fenders, and sidecovers to the original silver.
Towards that end I ended-up buying several different manufacturers paint and clear-coat and painting several "coupons" which I could hold beside the bike and compare the colors.
IIRC the Duplicolor engine enamel called "cast aluminum" with a clear-coat over it came the closest to a match.
I haven't resprayed it yet, tho, because of other more pressing, wage-paying projects.