Ah ha - looks like I can modify the UI:
setUI(new BasicProgressBarUI() {
protected Color getSelectionBackground() { return Color.black; }
protected Color getSelectionForeground() { return Color.white; }
});
This was a bit confusing, since the use of Foreground and Background weren't intuitive. Background is the color of the text when the bar isn't covering it, foreground is the color of the text when it is.
Here's the end result:
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…