Yep, wartime colours of both Packard and Rolls Royce Merlins were normally black overall. The supercharger housing has sometimes been seen in 'bare metal', but again, it was normally black, all paint being semi-gloss. Note that only Roll Royce produced Merlins had the RR name cast on top of each rocker cover - Packard-built engines had plain covers.
I'm pretty sure that the name of the color is "japan black", it being a really really dark blue. Something to do with Henry Ford's experiments with heat resistant paints early in the game, I think.
Or it could just be the voices again.