Ethnic non-whites became "free Negroes" and "Mulattos" in the eyes of the English by the simple process of marriage. There were three East Indian members of the Weaver family in Lancaster County and twenty mixed-race children of white women by "Negro" slaves in the same region. The Weavers married members of the Bell, Laws, Causey and Jones families, and the daughter of Aaron Weaver of Lancaster County married in Princess Anne County a member of the Anderson family, a descendant of freed "Negro" slaves. By the time the Weavers went West to establish the Weaver Settlement in Indiana, they were considered "free Negroes." See photos on my site:

http://www.freeafricanamericans.com/19th_4.htm
Paul