The original amber/orange bulbs lose their paint after they last a long time, so it actual doesn't matter what paint you use. Whenever the paint will come lose, it will be the amber paint (with silver coating) and not the silver paint only.

I used plain straightforward silver paint spray that can be used to give rims a "newer look".
I painted two new bulbs for my car, but you might as well paint the current amber bulbs (as long as the amber paint isn't loose already).

greetingz,

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1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)