In-universe explanation and theory of why Zion is mostly comprised of people of color.
So I see sometimes in YouTube videos about the matrix some people talking and asking about Zion and why most of the citizens and characters are seemingly mostly of African American descent. So I actually thought about it from the movies exposition and other behind the scenes sources and I think I found the most logical answer that has nothing to do with Hollywood or diversity cast and is purely in universe explanation.
We know from the architect that there were 5 iterations of the Matrix and the events of the movies take place in the 6th iteration and Neo is the 6th "the One" and the previous chosen ones had to fulfill the bogus prophecy the Oracle set to reset the Matrix before it becomes unstable. The Architect explained to Neo the role of the "One" is to reach the source, reset the Matrix, the machines wiping out Zion, but then the "One" has to choose 23 people to take out of the Matrix to repopulate Zion, 16 females and 7 males.
So with that knowledge, it's easy to assume that Neo's predecessor (the 5th "One") could've been an African American who chose most of the people to be other African Americans and maybe handful of other races, thus leading the Zion we know in the movies being mostly populated with people of color and mixed race and then other white people and other races gradually being taken out of the Matrix with time. It's also known that the role of Neo was offered to Will Smith, but he rejected, so I like to imagine that in universe, the 5th "One" could've been Will Smith.