gtk_widget_modify_bg has no effect when the theme uses pixmaps to fill in widgets

["Nix N. Nix" <nix go-nix ca>]

Hi!

When I set my theme to Smokey Blue, widgets that have modified
background colours using gtk_widget_modify_bg appear showing the
standard pixmap background instead of the modified background colour.
How do I turn off the theme-induced background pixmap ?

I tried to supplement gtk_widget_modify_bg with

style = gtk_widget_get_style (widget) ;
style->bg_pixmap[0] =
style->bg_pixmap[1] =
style->bg_pixmap[2] =
style->bg_pixmap[3] =
style->bg_pixmap[4] = NULL ;
gtk_widget_set_style (widget, style) ;

but it had no effect. What should I do ?