Here are a few possibilities, depending on what you're looking for:
The most obvious answer:
* Lord Voldemort: He wears black robes and has no hair, but is often associated with the color black.
Other characters who wear black and have hair:
* Bellatrix Lestrange: Wears black and has dark, stringy hair.
* Severus Snape: Wears black robes and has black hair.
* Sirius Black: Wears black clothes (usually jeans and a t-shirt) and has black hair.
* The Death Eaters: Many Death Eaters wear black robes and have dark hair.
To give a more specific answer, I need more information! Do you have any other clues?
For example:
* What gender is the character?
* What is their role in the story?
* Are they good or bad?
* Are they a student or a teacher?
Let me know and I can help you narrow it down!