The Christian victory at Lepanto in 1571 freed something like 10,000 European Christians who were galley slaves in the Turkish fleet.
However, I'm pretty sure the Arabs (probably descendants of Shem) were darker than the mix of Arabs/whites in North Africa who did most of the slave trading of Europeans. And I think it's safe to say the north Africans were probably a lot darker then too (before centuries of white sex slaves lightened up the gene pool and before many captured whites freed themselves from slavery by "turning Turk" and joining the pirates). As dark as Ethiopians? Nope. But I wouldn't be surprised if the north Africans then could pass for black today. The truth is we don't know.
If I had to guess, I'd say the old artist drawings of the Barbary Wars like this one best depicts the color of the north Africans from before the Ottoman slave trade. Of course, if I'm right, both blacks and whites have to eat a little crow about historical figures. This would suggest that "black" Simon of Cyrene who carried Jesus' cross was probably not as black as many black Christians make him out to be (Cyrene is in modern day Libya, not Eretria or Ethiopia or Congo). It would also mean that many of our early church fathers in north Africa (i.e. St. Augustine of Hippo) was probably a bit darker than white modern day Algerians.