Corrected entry: Kevin Costner is using a sledge hammer to take down the "Colored Bathroom" sign. That bathroom, according to Katherine, is in another building that takes her 45 minutes for a round trip. The sign he should have been taking down is the "Whites Only" bathroom sign in their building, so she can use that bathroom.
Corrected entry: When Katherine is blamed for long bathroom visits, she explains this by the absence of colored bathrooms in the building. After this scene Al Harrison is seen taking down the sign at a ladies bathroom and after this he says to Katherine "now you have a bathroom close to your desk." However, the sign that he takes down is 'Colored Ladies Room', a facility that was not supposed to be in the building.
Correction: They weren't in the same building. He knocked down the colored ladies' room sign in the building Kathrine goes to on the west campus.
Correction: Just because he takes down that sign doesn't mean he didn't take down the "whites only" sign offscreen.