UNIVERSITY CITY, Mo. — Tracey Wolff never had a problem with her 19-year-old son’s individualism: his “crazy” hair and unshaven face. But this week, his look suddenly seemed more worrying.

When she thinks of Trayvon Martin and his cropped hair and smooth face, Ms. Wolff says, she wonders, “If that can happen to the clean-cut kid who looks like a good student, then what’s going to happen to my son, who dresses sloppy?” She is considering talking to him about reconsidering his look.

“I don’t want to tell him how to dress,” she added. “He’s a grown man; do what you want to do, but keep in mind these are the things going on.”

On cable news programs and in protests around the country, the acquittal of George Zimmerman in the shooting death of Mr. Martin, an unarmed black teenager, in Sanford, Fla., has been fodder for an intellectual discussion on race and justice. But for many black residents, the verdict has spawned conversations far more personal and raw: discussions of sad pragmatism between parents and their children.