[ when Kaneki hears Bakugou, he approaches the door but doesn't open it yet, knocking first to let the other he will be coming in - so he can cover himself. Only after he hears that he can come inside is when kaneki does, having a look at Bakugou's hair.

Ah- right ] The hair is too dark. To get it back to your usual blond, we'd have to bleach it several times. Not in a row - you'd have to wait to bleach it again, or your hair could get too damaged.