Making the knob blink instead of the background poses a problem. The JScrollBar class doesn't let you access any attributes of the knob, so you can't change them. You could change the color of the knob through UIManager, but that would change the color of every knob on every scrollbar in the whole application. So if you wanted to do this, you would completely have to rewrite the JScrollBar class to allow you to set the color of the scrollbar knob.
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