Yeah my search is yielding the same results. Nancy Lanier and Thomas Jefferson.

Arkansas researcher, Mrs. James D. Reed (Doss) helped my grandmother in the 1980’s with our ancestry research project. The researcher obtained some records through the Arkansas History Commission. She was able to provide Green Berry Manuel’s son’s civil war records, 1860 census, and records pertaining to Green Berry Manuel’s daughter but there was no further information pertaining to Green Berry Manuel’s parents. 1980s research does state he was native etc

With Green Berry Manuel’s mother being Nancy Lanier, he might have been named after Benjamin Green.
Nancy Mills Lanier’s mother:
Susannah Lanier (Green) (1736 - 1809)
Birthplace:
North Carolina
Daughter of Benjamin Green
Wife of Benjamin Bird Lanier
* I found a document pertaining to the Plymouth Colony with a Benjamin Green. I didn’t research it any further than that.