Eva blinked. He really didn't know what she meant?
"Sebastian, we're fourth years now..." Any hint? No? she continued. "Well, remember when Alyss decided to tell me a few... interesting things about... your family? And she told me one thing... now I'm waiting for you to... explain it." not the best choice of words, but it would give him a clue about what she was talking.

"By the way..." she hadn't notice his hair until now. ".. you look a bit strange." It was odd to see him blonde. It was obvious Eva disapprove his new hair colour but didn't make comments about it.
Everybody was changing their nature hair colours. Who was she to criticise?