The answer
The priest’s hat is shaped like a dome, representing the fact that the priest belongs to the church. As for the black clothes, there are three types of people who wear black: the lawyers, the judges and the university professors. Thus the priest wears black because he is a lawyer who defends us before God, he is a judge who hears our confessions and gives us the absolution, and he is a professor who teaches us Christianity.
H.G. Bishop Moussa