Karen's Major Domo and closest confidant in Africa was Farah, the kind of devoted servant that makes you wonder if she should have just married him and been done with it. In the real world, this guy even visited her in Denmark after she had sold the farm, something we doubt Denys would ever do.
In the film, he's got her back the whole way. He's the mediator during negotiations with Chief Kinanjui, her nursemaid when she gets sick, and her Zen guide during tragedy (hello, lion attack):
FARAH: Msabu's bleeding. She does not have this ox. This lion is hungry. He does not have this ox. This wagon is heavy. It doesn't have this ox. God is happy, msabu. He plays with us.
When their camp is attacked in the night by lions, it's Farah who pulls the thorns from Karen's bloody back. Even more, he's not patronizing about it. Protective, yes, but only because he really wants her to make it. When Bror asks if Karen's ready to depart for her train (when she is leaving for treatment for syphilis), Farah indignantly replies, "She can come soon enough." Seriously: Bror was the guy who hired Farah, but it's Karen who he stays with once Karen kicks Bror out of the house.
In real life, Farah was a Somali, and in her book Shadows on the Grass, Karen explains that the Somalis were considered "superior in culture and intelligence" to the other tribes in the area.
As Karen prepares to leave Denmark for good, she gives Farah the compass that Denys had given to her. It means a lot to her, and so does Farah. She realizes that he's never called her anything but Msabu, despite their close relationship.
KAREN: This is very dear to me. It has helped me to find my way.
FARAH: Thank you, Msabu.
KAREN: I want to hear you say my name.
FARAH: You are Karin, Msabu.
In Karen's real-life memoirs, we learn a lot about Farah's life and his family. In the film, he's just Karen's devoted servant: no wife, no kids, nothing to distract us from his uber-faithful relationship to Karen.
Karen's memoirs suggest that she's very aware of the complicated relationships between the colonial masters and their native servants in Kenya. But aside from a few early blips, all we see in the film are two-dimensional African characters—even Karen's beloved Farah.