ARE YOU SAYING THAT RIETTE USED TO HAVE BLONDE HAIR???!?! ヾ(☆▽☆)

Girlie, that's just the lighting.

Both of them actually used to be brunette or atleast to be believed to have Bron hair in the novel, but after claiming the twin Dio Valeschesis' title their appearances changed alot. That's why yoojin when meeting Noah for the first time was so taken aback on how Noah could be related to Riette when they look so entirely different