FYI how would painting the chrome bit as well melt anything ? You guys really think that the bulbs are made of cheap parts as well as the chrome bits? They are built to withstand heat else no one would build them. Even if chrome was painted, only portion of heat will be absorbed if black paint was such a good absorber and doing 100% absorption instead of insulation in the walls would builders not just use black paint and be done.
Everything radiates back what they absorb (and i am sure the shiny material is build to withdstand excessive heating) its the law of physics because to every action there is equal and opposite reaction (that is the reason why a vehicle moves ).
And if anyone worried about melting the glass check this out .
Melting Point of Glass
The quartz surrounding a halogen bulb can withstand upto 900C and halogens cycle itself is at 250C .
So i think one should not worry about the reflectors.. some bits closers to the bulb might heat more than rest of the area but i am sure manufactures know that as well and accordingly build their reflectors.
Paint will most definitely do more absorption no doubt about that, but will it melt the reflector can only be figured out by actually doing a test so who is up for some testing with their headlights :p.