Superman, Wonder Woman, Thor, Spider-Man, and Captain America are some of the biggest names in comics. They are primarily red and blue. The red means they are bold, passionate, and determined, but grounded with blue's depth, wisdom and confidence. You might say Spider-Man is too angsty to be confident, but he does seem confident enough to crack jokes while cracking skulls.
If you add the yellow accent of the first three heroes, you see they are attentive, provide safety, joy, and are a little bit ostentatious. Yet, ostentatiousness is something that probably doesn't apply to the other two. The white of Spider-Man's eyes and Captain America's midriff shows that they are more pure and innocent, rather than flashy.
Other examples of red and blue include the Atom, Giant Man, Ant Man, Power Girl, Captain Marvel, Ms. Marvel, and Doctor Strange.