pygtk theme colors ?

[manatlan]

I understand nothing ...
I'm trying to get the color of a normal background window

and when I change my themes (i switch between a light and a dark
theme)
i obtain always the same output below :

style = gtk.Button().get_style()
l=[gtk.STATE_NORMAL,gtk.STATE_ACTIVE,gtk.STATE_PRELIGHT,gtk.STATE_SELECTED,gtk.STATE_INSENSITIVE]
for i in l:
    print "- base",i,style.base[i].to_string()
for i in l:
    print "- text",i,style.text[i].to_string()
for i in l:
    print "- fg",i,style.fg[i].to_string()
for i in l:
    print "- bg",i,style.bg[i].to_string()

what's the trouble ?!?