Blond for now, but it turned red, when she grew older in her first life, and she found the first sings of it turning red again.
Her father called it a curse and imprisoned her in the attic, that's why she is afraid of it turning red again. One of the reasons she ran away from home and got engaged to the wolf clan.
Spoiler:
The red feathers/hair may be a sign of her being a special kind of bird, like a phoenix.
I didn't get that at first either, but then they mentioned the molting of the birds, and THAT makes total sense. Birds are either really ugly or cute and then completely transform after they shed their fluff and grow actual feathers.
?