Eumelanin is a working shield, not just a colour

Eumelanin sits in caps over the nuclei of skin cells and absorbs ultraviolet light before it reaches DNA, and it also quenches the free radicals that light creates. Pheomelanin does neither well and can even generate damage under UV, which is why red-haired, poorly tanning skin carries the highest skin cancer risk. The same receptor also drives DNA repair and antioxidant defence inside the melanocyte, beyond pigment alone. That is the real biology behind the word photoprotection: more eumelanin plus better repair equals less damage reaching the genome.