Better update your history of the Luo tribe from which O came. It goes back to Arab.
The Luo are not Arabs. They are Nilotic.
People have had sailing down to a tea in that region for thousands of years.
Light skin doesn't last there. Dark skin survives well, and the further South you get to the Equator, the darker the better.
It's hypothesized it's a skin cancer prevention syndrome ~ Arabs, however, are descended from populations that arose in the Arabian peninsula as well as Armenian type people who lived around/near the Black Sea. ~
That you have black African Luo with Nilotic origins living in the same place (Mombasa, Tanzania, Kenya) as far lighter Arabs and Jews and Englishmen is no more surprising than the fact you can find similar mixes in New York City.
For a variety of reasons these groups maintain a certain level of genetic continuity ~ cousin marriage is one of the reasons.
At the same time you wouldn't be surprised to find New Yorkers speaking New Yorkese irrespective of their racial origins you shouldn't be surprised to find people in/near Mombasa speaking Arabic, or even PORTUGUESE.
Doesn't turn the Luo into Arabs, or Portuguese, or Englishmen!
He really doesn't look terribly Arabic. Neither did his grandparents in America. They don't look Arabic at all ~ very Western and Northern European ~ they've even got some Scandinavian ancestry! The jaw, though, is pretty much Viking.