I think a poster(getinthetruck) touched on it earlier that their two groups of Arabs:
Qahtani- pure/original Arabs, southern Arabs like the kind found in yemen
Adnan- Arabized, northern Arabs, people of north Africa and Levant
Qahtani Arabs in the American sense might be considered black, but not really in my view, although I will say most people in the "Arab world" consider them cousins of Abyssinians. I can tell alot of posters never been to middle east because there is so much strife between historical and modern day Arabs, that there is no clear answer of who is an Arab, other than if your father is an Arab your considered an Arab.