Astor is an old black man who works for Mrs. Shortley. He's been on the farm since the days of Mrs. McIntyre's first husband, the Judge. Because he's been there longer than even Mrs. McIntyre, he has a position of some authority on the farm, though Mrs. McIntyre considers black people so much beneath her that she doesn't allow Astor to communicate with her directly. Astor, however, finds ingenious ways of communicating. And overall he seems like a good person.
Our biggest sign that he is a good person is his relationship with the peacock. While O'Connor's religious vision as played out in her fiction can be confusing, her stance on peacocks is not. For O'Connor, a character who loves peacocks and recognizes the magnificence of peacocks is probably a nice person. (Go to "Symbolism, Imagery, Allegory" for more on that.)