The input area works off of two StyleVars: input_background and control_focus_background. The first is before the user selected the input area, and the 2nd is while the user is typing.
The actual shouts' background area works off of the postbit_background StyleVar.
Right, so you would have to edit these StyleVars: input_background and control_focus_background. The first is before the user selected the input area, and the 2nd is while the user is typing.