For the purpose of making Islam attractive to black people, and to support that Islam is the natural religion of Africans - in contrast to Christianity as the religion of the slavers (cf. Christianity, Islam and Slavery) - some have claimed that Muhammad was a black (African) man. This has no factual basis.
Muhammad enslaved people, owned and sold slaves, including several black slaves.
As the last two hadiths show, the statements about his white color are not absolute but a relative ones. He was not white as chalk, nor did he look like a Scandinavian. It means that among the people of Arabia, he was discernably of fairer complexion than most people around him. Otherwise, the above referenced hadiths where he is distinguished from his companions as "the white man" would not make any sense. Muhammad was not a white Caucasian but a Semite of relatively fair complexion, an Arab, and not a black African man.
Black skin and Judgment Day:
And on the Day of Resurrection thou (Muhammad) seest those who lied concerning Allah with their faces blackened. Is not the home of the scorners in hell? (Az-Zumar 39:60)
Muslims usually try to understand these verses as being metaphorical without racist connotations.
However, there are some hadiths that link black skin and creation with judgment day:
Narrated AbudDarda'
Allah's Messenger (peace be upon him) said: Allah created Adam when He
had to create him and He struck his right shoulder and there emitted from it
white offspring as if they were white ants. He struck his left shoulder and
there emitted from it THE BLACK OFFSPRINGS as if they were charcoal.
He then said (to those who had been emitted) from the right (shoulder):
For Paradise and I do not mind. Then He said to those (who had been
emitted) from his left shoulder: They are for Hell and I do not mind.
Transmitted by Ahmad. (Al-Tirmidhi Hadith, Number 38- ALIM CD ROM Version)
For these traditions, it is much harder to resist the impression of racist overtones. They do not speak about people being whitened or blackened at the time of judgment, but link their original skin color with their eternal destiny, i.e. Allah decreed that blacks will enter hell in contrast to whites.
In fact, other narrations even command that any person claiming that Muhammad was black be put to death!
Ahmad ibn Abi Sulayman, Sahnun's companion, said that whoever says that the Prophet was black IS KILLED. The Prophet was not black. (Ibid., p. 387; capital emphasis ours)
The Nation of Islam teaches that white people are devils. Their members might want to ponder this statement by Muhammad: