Xrefresh is a simple X program that causes all or part of your screen to be repainted. This is useful when system messages have messed up your screen. Xrefresh maps a window on top of the desired area of the screen and then immediately unmaps it, causing refresh events to be sent to all applications. By default, a window with no background is used, causing all applications to repaint "smoothly." However, the various options can be used to indicate that a solid background (of any color) or the root window background should be used instead.
-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(3).
-display display This argument allows you to specify the server and screen to refresh; see X(3).
Black, White, Determines what sort of window background to use.
Geometry Determines the area to refresh. Not very useful.
DISPLAY - To get default host and display number.
It should have just one default type for the background.