Found a piece talking specifically about Duval and Anson...written by David Fleitz (SABR member, author)
https://www.baseball-almanac.com/corner/c042001d.shtml
"His autobiography, written in 1900, made no mention of Moses Walker, but related in gleeful detail how the team treated its "mascot", a black man named Clarence Duval whom Anson described as a "coon" and "a no-account n-----." Historian Bill James says that "they treated Duval exactly as one would treat a dog." Anson made no secret about his feelings about sharing a field with blacks, repeating the statement "Gentlemen don't play baseball with n-----s" to anyone who would listen. People listened to Cap Anson, the towering figure of baseball in the 1880s."