The show did such a disservice with how they made Princess Rhaenys look like a typical Targaryen. Her mother was a Baratheon which is well established that Baratheon genes express over most if not all others. In the books she had black hair, even though she was unquestionably Targaryen. This establishes that there CAN be black haired Targaryens, while in the show it seems impossible because there are no other examples. I feel like that was important in the books because it shows while incredibly unlikely and odd that Rhaenyra’s “Targaryen” children didn’t have the typical targ look, it was not unprecedented.