Take a look at the complimentary colors combinations on the left. Did you happen to think of the Hulk, or Superman? Comics, being a printed medium, are designed in CMYK, on which that color wheel is based. It seems pretty clear, to me at least, that a number of famous super hero's costumes were designed with the use of the complimentary colors of printing. I imagine it would simplify your printing costs when most of your character stable was made of simple primary colors.