... as I struggled to understand my Y-DNA match (a type of DNA test that only seeks a man's all-paternal cousins and ancestors) to a man of color.
I assumed the worst initially -- that my paternal ancestors must've been slave owners at some point in the past, despite no records of any slaves in the late-1700's and early-1800's. They were Methodists too, who were more likely to oppose slavery during that time (until that religion spread more into the South).
I finally contacted my Y-DNA match, who had separately traced his paternal ancestors to the same location as my paternal ancestors-- Loudoun County VA in the mid-1700's. That's where he'd hit a brick wall, just like me.
His assumption was that the parents (or parent) of his brick wall ancestor was black, given how that ancestor was listed as colored or "mulatto" in later census records. And that's where the last episode of season 2 (S02E10) of Finding Your Roots was helpful to us. That episode was about Henry Louis Gates' ancestry, and his white ancestor who had married a black woman despite how it was illegal in Virginia at the time. Thereafter, that white ancestor of Gates was listed as black or mulatto in census records! Gates said something like, "So they made the brother black!" (For marrying a black woman.)
My 5th cousin (once removed), which is a CLOSE MATCH in terms of shared genes on the Y chromosome (since they don't get mixed with genes from female ancestors), was instead always listed as white whenever he paid his yearly taxes! It was only on census records that he'd suddenly be listed as a black man.
To shorten this post, I'll just cut to the chase. What me and my cousin deduced was that his brick wall ancestor was indeed a white man, and his two brothers (one of whom was my brick wall ancestor) had moved away together as his ancestor (the oldest brother) remained in Loudoun County VA a few more years. He was a deputy sheriff there UNTIL he married the black woman, when that position was stripped from him (without an explanation provided in the records). He thereafter moved away (after my ancestor had already moved) to live with his wife and children in the SAME community of "free mulattos" where Henry Louis Gates' white ancestor had also moved with his family!
And we both broke through our genealogical brick walls, learning that the father of our paternal ancestors was a Quaker from New Jersey who had moved to a Quaker community of Loudoun County VA in the mid-1700's, at a place called Goose Creek.