:I know of no Colvins who were slaves. There was an Alfred Hardwick Colvin, born 1807 in Chester District South Carolina. He was the son of Andrew Feaster and Jemima Petrie Colvin. He came to northeast Ala. in 1835 with his bride, Lucy Crosby. They entered land in Benton County/Calhoun. Perhaps this will provide a lead to your branch of the Colvin family.
You might also check Cherokee enrollmant records, or "Cherokee by Blood" for clues to the Colvins.

James Nickens
Virginia Indian Heritage Assn., Inc.