Changing background and foreground of a widget

[Kent Schumacher <kent structural-wood com>]

Hi,

How do you change the background and foreground colors of a widget?

I've looked through the archives and seen this question asked several
times.  Both the FAQ and the archives seem to indicate that the answer
is to change the resource file.

This will not work for me because I am having a user pick specific
color schemes and they have to be able to dynamically see the 
combination of foreground and background.

I have looked at the multiplicity of gtk_style* calls, but without
documentation their operation is too opaque...

Help!
Kent