If your thought is "Mainly black with red accents", then that's what you do... but just doing the wheel cap red looks like an afterthought or an "oh well, that's just how they came and I'm stuck with it..." If you are going for totally murdered, that's not going to work.
I recommend you accent with red in other places to make the truck look more balanced. You might try doing the grille eggcrate in red... the door handles... badges... accents on the cowl. NOT the wipers... That's ghetto! Just not too much... Kinda "sprinkle" the red around. Maybe you can photoshop a few things to see what you like before doing it.