I use Permatex Aviation Form-a-Gasket.
The colour is Chevrolet Orange. Back in those days each GM Division had their own colours.
All water pumps are installed at the time the engine is painted. The water pump casting number may be partially to totally obscured. The fan clutch moutning hub has only four threaded holes. The pump bypass hose and clamps, if equipped, may appear with orange or silver paint overspray.
(NCRS Judging Guide - 1967 Corvette)