Yup, DarthRacer is right. Manifold paint from an auto supply store. You can also use BBQ paint if you want it black. No, you do not prime it. The primer will burn. Just clean it really well with rubbing alcohol and scuff it with steel wool or a Scotchbright pad.
There's a potential problem with it not being fuelproof, though. It might work fine, but since I haven't done it, I don't know if the fuel will eat it.