Must be to many years of tabletop Mech games but I always end up pairing blues/blacks with red. Though to be honest, what's good for a Crusader probably wouldn't be good for a book cover.
Well, unless you're reading a LOT of Drake and Ringo.
(Now that I think about it, most of my color pairings are industrial in design. I gotta get new lines of work and recreation. Even my computer case is yellow/black!)