Do you know if Chapan's eyes will fill in with cold when he gets older?
I’m assuming you meant something else and not cold? Buuut either way i think i know what you mean? Correct me if I answer this wrong.
I don’t think the color of Chapan’s eyes will change at all as he ages, actually. The black sclera and white irises is due to his shadow powers, and not his albino state (though the albino state and his powers are tied. his abilities are the cause of his coloring, not the other way around). Because of this, I doubt they’ll change.
However, if he for some reason lost his shadow abilities, the sclera of his eyes would fade to a dull yellow with red-tinged irises. Because he was born albino, I doubt he would suddenly not be if he lost his powers, but the effect on his eyes would go away.