Setting window color in slave mode

Have looked at the docs and set there are config settings that enable a user
to change the color of the GUI window (from green to another color).

Is there a command that may be communicated to mplayer when in-slave mode to
effect the same change.

Currently, the -wid command is used to place the output in a Tcl\TK window.
However, the background is green and it would be preferable if it could be
changed to another color.

Rick