Just my experience.
I painted my 1st one body color and my engine was black.
While changing plugs or a plug wire one day i accidentally shoved one of my master cyl lines over and it started rubbing my steering shaft.. Short version..I rubbed a spot on brake line and fluid shot all over fenderwall. Peeled all of the pretty paint off.
#2 bronco that is my sons.
I used POR in the entire engine bay and oil grease dirt etc just wipes or rinses right off. Chemicals dont effect it like regular solvent based paints.
So I will use POR in engine bay from now on
They have grey or black in POR and you can top coat them but paint would still peel off the POR if you got a bunch of brake fluid on it.
I put it on new metal parts but you have to use their etch first.
Just something to think about...but i do like body color better
Chuck