well i'm glad ur going the way of powdercoating. i have my valve cover powdercoated. love it. and i don't have to keep it shiny like a polished finish.
of the colors mentioned, i would definitely not go with white. i don't know anybody who does white, but white is never an accent color, only if its against black, and ur car ain't black.
ya, everyone does red, so scratch that. but i would do with what would look good under your hood, rather than straying from "what everyone else is doing." for me, i've decided to go with a dull metal look. still clean looking, just not shiny. here's a shot of my engine.
so if i were you, i'd just look at other people engine bays (white cars, perhaps) and see what you like. perhaps post some pictures here for everyone to compare.