Yes. The illustration portrait of a black man wearing a suit and holding that 'thing' on his hand clearly expresses that the person is a politician or a leader. In this case, it would refer to Remi. The conflict between religion and tradition is evident because Remi wanted to bring to an end the fight between the two and also to get rid of tribalism. He acted as both a leader and a politician both in the Christian religion and in politics.
Colours also symbolize something but I'm sorry I'm not conversant with the meaning of many colours used in covers of literary books.
The name 'The Black Hermit' also reflects the themes in the book. Remi running away from the village only to realize later he can't run away from his people and the tribe. He realizes he was meant to be a leader and a politician which are qualities he possesses. As an educated person, he can well present his tribe in the government or be appointed in a government position for the benefit of his tribe.