I have painted lots of them for special effects.
One of the treatments we used to use for street rods was to first chromate the zinc-alloy carburetor bodies for protection, then paint them with black epoxy paint. The steel items were then chromed; so the finished product was a splash of chrome against a glossy black background. Here is a sample:
http://www.thecarburetorshop.com/Edelbrock_X2_side.jpgRemember, with any painting, wear appropriate breathing apparatus.
For those interested in the painting: after the bodies were chromated (did not paint the inside, and the paint will NOT protect the inside of the bodies), all threaded holes were masked to prevent paint getting in the threads, and the bodies painted. Once painted, the masking was carefully removed, and the bodies baked at 125 degrees F. for 30 minutes in an ELECTRIC toaster oven (DO NOT USE A GAS OVEN WITH FLAME!!!!!). Remember that epoxy does not dry, it sets; so the heat tends to even the flow.
If you look closely at the picture, you can see the green of the chromate on the surfaces where the aircleaners attach.
Have done other carbs in other colors to match engine color for some customers.
Epoxy paint is not required (although I do like it). I would guess any good high temperature engine paint, baked on, would suffice.
Don't get carried away on the baking temperature. Zinc alloy will "slump" at about 450 degrees F.
Jon.