Comic hero colors

Yesterday, I posted something about the Marvel special I watched. I posted a picture of Marvel superheroes to go with it.
Afterward, I looked at it and thought: why do almost all the superheroes have red and/or blue costumes? With a little black or brown thrown in.
The Hulk really stands out in his green skin.

This includes Superman (who wears blue andred) and Batman, who wears black. The X-Men don’t, but they mostly wear regular clothes.

It’s almost like there is an unofficial superhero uniform. Isn’t that strange?