The fix for 6451939 tried to be careful about when colors were replaced by checking that the existing background was one of the known colors for the component. Unfortunately, even this isn't enough. In some cases, JLabel uses the same background color as one of those that the text components know about.
For now, we haven't yet determined an optimal way to solve this problem. So we'll stop replacing the background color altogether for JTextArea. A new bug will be filed so that we can solve this problem in a better way.