I used some testors model spray paint that was supposed to be chrome. so far it has held up fine, I would think pretty much any silver paint would do. Temp might be a concern, but I havent had a problem yet, and for the few dollars it costs for bulbs, I have spares handy for when I need em.
In anycase, the orange bulbs, orange is only painted on to the bulb, so it really doesn't last too long anyway. But the silver paint still looks just like I painted it two months ago.