Pure blooded Sub-Saharan Africans can have a skin color that is almost black. When a very dark African stood next to a pale European, the two appeared to be black and white, and that's what the...
Where and when would be helpful in answering this question. In tribal Africa, it was most often other tribes of black people. At earlier times in the US, it was white people. Now it could be anyone.
Any person should be addressed in the same manner: If you know them well: By their first name If you know them professionally: Mr. Mrs. Dr. Professor Reverend Rabbi Sir Madam (or other title accorded...