People of African descent were categorised as racially inferior, so they were forbidden from marrying ethnic Germans, but apart from that they were largely left alone. There were just so few of them in Germany that it never really occurred to the Nazi leadership to bother with them; there were probably under thirty thousand blacks in Germany. All through WW2 blacks living in Germany went to school, held jobs, even served in the army. It helped that most blacks in Germany were well assimilated - by far the greatest source was Germany's African colonies. When Germany lost them after WW1, those blacks with the strongest connections to Germany were the ones who emigrated. So although blacks were regarded as inferior, they were generally not hated or regarded as enemies in the way that Jews were.

The exception to this were the so called 'Rhineland bastards', who were mixed-race children left over from the French occupation of the Rhineland after WW1 (the French used some troops from their African colonies). This was doubly offensive to the Nazis, since it was not only miscegenation but collaboration on the part of the mothers. Hitler ordered them sterilised, but they weren't sent to concentration camps; even the sterilisation was done in secret, with many children not being told what was being done to them. About 400 children and young adults were sterilised overall.

There was no official Nazi policy for black POWs, so it came down to the commander in the field. There were a few instances of summary executions, but then again Germans also did that with white prisoners on occasion. Usually blacks were sent to segregated POW camps, but they received worse living conditions which contributed to a higher death rate (particularly towards the end of the war as German food supplies collapsed).