code: def palette_font_and_background_color_toggled(self, settings, key, user_data):
          
          self.settings.styleFont.triggerOnChangedValue(self.settings.styleFont, 'palette')
docs: If the gconf var use_palette_font_and_background_color be changed, this method
          will be called and will change the font color and the background color to the color
          defined in the palette.