changing Gtk::ComboBoxText text color

[<tony_silva alum mit edu>]

I've created a class StatusComboBoxText, derived from
Gtk::ComboBoxText, that is intended to change its base and text colors
depending on the currently selected value.  I can already change the
base color in this manner (using Gtk::ComboBoxText::modify_base()) but
not its text color (using Gtk::ComboBoxText::modify_text() or any
other method).  The simple test program attached below summarizes what
I've tried.

I'd greatly appreciate any clues on what I'm doing wrong.  I read the
API manual, tutorials, and FAQs, searched for "ComboBox* and color*"
in "All mailing lists" at mail.gnome.org, and searched for "ComboBox
color" at bugzilla.gnome.org but am still stumped.

I'm using GTKmm 2.8.2 and GTK+ 2.8.9 on a Windows host/target.  Since
this may have as much to do with GTK+ as GTKmm, I'm posting this
question to both lists.

TIA,

-- Tony

-----------------------------------------------------------------------------
// change Gtk::ComboBoxText base and text colors

#include <gtkmm.h>

int main(int argc, char** argv)
{
  Gtk::Main kit(argc, argv);

  Gdk::Color baseColor, textColor;
  baseColor.parse("yellow");
  textColor.parse("red");

  Gtk::ComboBoxText comboBoxText;
  comboBoxText.append_text("some text");
  comboBoxText.set_active_text("some text");

                                // this changes the base color:
  comboBoxText.modify_base(Gtk::STATE_NORMAL, baseColor);

                                // none of these change the text color (when
                                // done either before or after append_text()):
  comboBoxText.modify_text(Gtk::STATE_NORMAL, textColor);
  comboBoxText.modify_fg(Gtk::STATE_NORMAL, textColor);
  comboBoxText.modify_bg(Gtk::STATE_NORMAL, textColor);

  //comboBoxText.append_text("some text");
  //comboBoxText.set_active_text("some text");

  Gtk::Window window;
  window.add(comboBoxText);
  window.show_all();

  kit.run(window);
  return 0;
}