Canonically literally every Space Marine (except for the Blood Angels IIRC) should have dark skin when exposed to sunlight and then (except for the Salamanders) flash to an unnatural pallor when they step inside, because one of the mutations they get is photochromic skin to protect them from getting sunburns while still ensuring they get enough vitamin D. That sounds incredibly stupid and like I just made it up but that is the actual canon from the lore, along with Space Marines eating their enemies brains to gain their knowledge and having acid spit like the xenomorph.
Warhammer 40K is a very silly franchise and the art direction does it a disservice by not leaning into it more.