The science of why Superman would need dark-colored skin to power his special abilities.
Superman should be black.
By that I mean he should have dark skin, and not that he’s African-American or any other person of color. After all, the Man of Steel is from the planet Krypton, not Earth.
In the movie Man of Steel, Superman asks his biological father why he’s different from humans. As Jor-El explains: “Earth’s Sun is younger and brighter than Krypton’s was – your cells have drunk in its radiation, strengthening your muscles, your skin, your senses.”
Photosynthetic species – including a Kryptonian like Superman – living on a world orbiting a relatively inactive star would need dark pigments to harvest light.