Try use xdpyinfo, it returns 16 different visuals from my solaris system.
( May vary with different systems. ) but if use

       GraphicsConfiguration[] gc = gd[0].getConfigurations();
       gd[0] is X11GraphicsDevice[screen=0]

only 11 visuals returned back and can be used for creating non-default canvases.
This can be easily seen by run gfx.java.
You can find this file in /home/jdu/qing/nodefault/4181880