We know that it is explained that Roxas hair is blonde because of Ventus. But, has it ever been explained that why Xion's hair is black? Yeah, Xion's appearance depends on other person but if Xion resembles Kairi, why is it not just brown then? As far as I am concerned, there is no one that is related to Sora before the adventure has black hair and of course Roxas. How if the black hair is because of Ven's deep memory that he is grateful to Skuld for whatever happened since the dark road also seems to have her possibly in it . Well, I don't think Nomura has thought this before but he could just put up a plot twist like this like Ventus and Roxas, right?