setting font for a GtkComboBox

["Zvi Sebrow" <zvi sebrow verizon net>]

I am try to set the font and colors of  a GtkComboBox in response to another event.
for a GtkComboBoxEntry, I can use  GTK_BIN(combo)->child , but what do I use
for a GtkComboBox.  
using gtk_widget_modify_font(combo) doesnt seem to do anything.
since this is done dynamically, i dont think RC files will work.

also, how do i change the font/color of the popup list.