How to make no color

[Jiang XU <jiang xu echostar com>]

I set up the background of a GtkWindow.  I wonder whether there is a way
that I could set the widgets in that window with no color.  Which means
I can see and use the widgets in the window, but I want it to be no
color so that what it will be shown on screen is like absolutely
transparent and you can see the background area which is covered by the
widgets.

If someone knows whether there is such a way, please teach me.  Thanks