Yeowe and Werel
Yeowe and Werel are the third and fourth planets, respectively, of a single star system described in Four Ways to Forgiveness. Yeowe was settled from Werel, which has no connection with Werel / Alterra. The dominant race of Werel have black or bluish skins. They have enslaved the white-skinned Werelians as well as the children of unions between slaves and masters, who are described as having "clay-coloured" skins.
A later short story titles "Old Music and the Slave Women" which appeared in The Birthday of the World deals with a civil war on Werel. In this story it is explained that the white-skinned Werelians, known as "dusties" are the remnants of an ancient, vanquished culture. At this point so much rape or concubinage of slave women has occurred that there are very few people with white skins left.
Read more about this topic: Planets Of The Hainish Cycle