Well, for what it's worth, Memory Alpha states:
"In the teleplay, however, only Lutan's guards were specifically written as being African. It was director Russ Mayberry's idea to make all the planet's occupants African. Disgusted by this decision and Mayberry's attitude towards the performers, Gene Roddenberry fired Mayberry late in production. The remainder of the episode was directed by an uncredited Les Landau."