OK - searched the archives for tattoo & sunburn and didn’t find any references except how getting a tattoo felt like a sunburn.
In my case, my tattoo was pretty effective sunscreen.
I’ve got an armband (of entwined “christian” fishes) on my left arm and a large multi-colored phoenix on my right. After a weekend outside, my arms are burnt and peeling except where my tattoos are. Strange.
I would’ve thought that the darker pigment would’ve absorbed more sun and gotten burned worse. Then I started thinking about black-body radiation and now I’m of two minds on the possibilities - probably neither one right.
So - for you physicists (or dermatologists… or tattooists) out there, any straight dope?