-white
Use a white background. The screen just appears to flash quickly, and then repaint.
-black
Use a black background (in effect, turning off all of the electron guns to the tube). This can be somewhat disorienting as everything goes black for a moment.
-solid color
Use a solid background of the specified color. Try green.
-root
Use the root window background.
-none
This is the default. All of the windows simply repaint.
-geometry WxH+X+Y
Specifies the portion of the screen to be repainted; see X(7).
-display display
This argument allows you to specify the server and screen to refresh; see X(7).