65 Valiant engine color.

As I understand it, the exhaust manifolds were on the engine when it was painted. The manifolds were not specifically painted, but the inch or two or three next to the heads got engine paint on them. That paint would burn off in just a few minutes running, so basically they ended up unpainted and were soon covered with surface rust and were brown. Not especially attractive that way, so most today paint them with some kind of high temp silver/gray exhaust paint.