What does TJ's facial expression reveal about him when MrBarnett stops helping him and starts helping the white customer?

TJ is perturbed but doesn't make a big deal of it, he is used to this treatment. Cassie is incensed and, after an hour of waiting, marches over to Mr. Barnett and demands to be attended to. Cassie is much more assertive than TJ. She understands what's going on but believes in the principle of the situation. Despite the overt racism, Cassie stands up for herself.