Responses
As I said before, could be a way to throw us off. And if we also put your purification into theory, it could be the darkness(I cannot recall what it is in him rn) that physically changes him entirely from skin and hair. So maybe is asya's treats has an effect on him, skin would be the biggest factor?
I see everyone saying he's getting whiter and whiter, but I actually have a theory. It could also be from his human blood. Remember how the story was based off a noctis elf and human?? What if it was about his parents, or a story that human and elves can have children together?? Maybe Ivan's human traits are coming in and this is the first sign of it and the author used the skin so we would all be thrown off by it?
Ofc this is literally just a theory and it could be a whole genshin impact situation but who knows?