Using SwingSet2's JInternalFrame demo, selecting GTK L&F and then changing it to other L&F, the color of the background of "JinternalFrame generator" window is not changed and stay same as GTK's one(gray).


To reproduce,

1. Launch SwingSet2 demo and you can see JInternalFrame demo is selected.
2. Change L&F to Motif L&F. There is no probelm.
3. Change L&F to GTK and the background of "JInternalFrame generator" is pale gray.
4. Change L&F to Motif L&F again, then you can see the problem.
   The color of the generator is not changed and stay same as GTK though the color of buttons, checkboxes and textfield is changed properly.
* The image is attached.


It's not so remarkable on Java L&F, but the problem is seen.
It's seen in b13(I saw this problem also in b11 and b12).

I saw this problem on both of windows and solaris(sparc/IA).