I can’t answer the question but it might depend on the superhero age you are trying to simulate. I would think BRP/Mythras supers would do Iron Age gritty just fine. Not sure about 4 color though.
Plus there are only 3 or 4 BRP superhero games out there that I know of, SuperWorld, Agony & Ecstasy , the new Mythras book coming out and Elder Godlike. Not a lot of choices!