Well, there's this cool thing you can do with layer blend modes.
Look at this episode of my comic - https://tapas.io/episode/1161541
(Yes, self-promo mixed with advice >.< but honestly I'm trying to help)
- In the first four panels, I colored the characters using the same color palette each time.
- However, it would look unrealistic if their colors were the same in each panel, since the lighting is totally different.
- Therefore, I created a separate layer, put it on Overlay blend mode, and set it to around 50% opacity. Then I clipped that layer to the color layer and quickly colored in the characters in each panel with the color of the lighting in that panel.
- The result is that the characters' colors look a lot more natural and integrated with the surrounding light. Meanwhile I still get to use my simple color palette; it's really convenient.
Also, learn how to use the curve adjustment tools if you haven't already. Super useful.
Also, I don't know how well this fits into the '50s superhero comic' aesthetic, but consider trying to use a limited color palette (not too many colors). It tends to give a really pleasing look. For examples, look at "Unfamiliar" by Haley Mewsome, "Leftovers" by Dawgofdawgness, and/or "You Reside Under My Wings" by Crowwithashortcake.
Hope some of that was helpful 
