SOLVED. YA fantasy male main character believes he's becoming a monster and somehow golden apples are involved? [s]

[Sentory]

Last read in early 2000s (or maybe 1999?), so I don't remember much. It was in my middle school library. Book cover was hardback with a plastic dust cover - I vaguely remember a mostly blue cover with gold. Maybe a blue background with a golden apple/apple tree foreground

Plot
Dual heritage, eyes indicate other heritage
blue eyes = crazy

Paintings of ancestors, realizes a painting has eyes painted over, scrapes brown paint off to see eyes just like his

Coming of age quest/journey through mountains? Main character somehow ends up in a massive deer skull with the golden apple tree

[Cupcakedoll]

It's been a long time since I read it but I feel like some of the details match.

[Sentory]

Yes! Thank you! This has been bugging me for years!