They couldn't be citizens, given that they weren't racially German (I'm not sure how the Nuremberg Laws would be applied to mulattoes). But it's not like they were discriminated against, like they would be in America. Jesse Owens wrote about this.

Arguably, their treatment was the same. Black Germans underwent forced sterilizations or cruel mistreatment. At worst, German society didn't think much of their African populace, but the ones they captured in war were subjected to inhumane conditions compared to Whites.

https://en.wikipedia.org/wiki/French_prisoners_of_war_in_World_War_II#African_and_Arab_prisoners

Unlike their white compatriots, the colonial prisoners of war were imprisoned in Frontstalags in France rather than being brought to Germany.[9] By keeping colonial soldiers in France on the pretext of preventing the spread of tropical diseases, the Germans also wanted to prevent the "racial defilement" (Rassenschande) of German women outlawed by the Nuremberg Laws of 1935.[31] Black troops were treated worse than their white compatriots, and some of them were used for "degrading" anthropological experiments or subjects of medical testing into diseases.[33] Although the living conditions for black soldiers gradually improved, they were still considerably lower than those of white French soldiers. The mortality rate among black soldiers was also considerably higher.[33]