How to make the toolbar button flashing

["Miroslav Rajcic" <rajcic sokrates hr>]

I am trying to make the "Pause" button flash (or show any similar behaviour 
similar to that) when the pause state is active.
So far I tried many things, but none of these seem to work:
- changing the button background color
- changing the button stock icon
- changing the button relief style

Relevant code is following:

//start timer to alternate the button state
nBlinkButtonTimerID  = g_timeout_add (900, flash_pause_button_timer, NULL);

gboolean flash_pause_button_timer(gpointer data)
{
static bool bFlipFlop = false;
bFlipFlop = !bFlipFlop;

//get pointers to the relevant buttons
GtkToolbar *toolbar2 = (GtkToolbar *)lookup_widget(window1, "toolbar2");
GtkWidget *tool_pause = (GtkWidget *)gtk_toolbar_get_nth_item(toolbar2, 2);
GList *children1 = gtk_container_get_children(GTK_CONTAINER(tool_pause));
GtkButton *button = (GtkButton *)g_list_nth_data (children1, 0);
g_list_free(children1);
GtkWidget *tool_stop = (GtkWidget *)gtk_toolbar_get_nth_item(toolbar2, 1);

//create two alternating colors (standard bkg and black bkg)
GtkStyle* style = gtk_rc_get_style(tool_stop);
GdkColor rgbStart = style->bg[GTK_STATE_NORMAL];
GdkColor rgbEnd = { 0, 0, 0, 0 };

//modify color
gtk_widget_modify_bg (GTK_WIDGET(button), GTK_STATE_NORMAL, (bFlipFlop)? 
&rgbEnd : &rgbStart);
gtk_widget_modify_bg (GTK_WIDGET(button), GTK_STATE_ACTIVE, (bFlipFlop)? 
&rgbEnd : &rgbStart);
gtk_widget_modify_base (GTK_WIDGET(button), GTK_STATE_NORMAL, (bFlipFlop)? 
&rgbEnd : &rgbStart);
gtk_widget_modify_base (GTK_WIDGET(button), GTK_STATE_ACTIVE, (bFlipFlop)? 
&rgbEnd : &rgbStart);
gtk_widget_queue_draw (GTK_WIDGET(button));
#if GTK_CHECK_VERSION(2,18,0)
gdk_window_process_updates (gtk_widget_get_window(GTK_WIDGET(button)), 
TRUE);
#else
gdk_window_process_updates (GTK_WIDGET(button)->window, TRUE);
#endif

/*
GtkWidget *w1 = 
gtk_tool_button_get_icon_widget(GTK_TOOL_BUTTON(tool_pause));
gtk_widget_modify_bg (w1, GTK_STATE_NORMAL, (bFlipFlop)? &rgbEnd : 
&rgbStart);
gtk_widget_modify_bg (w1, GTK_STATE_ACTIVE, (bFlipFlop)? &rgbEnd : 
&rgbStart);
gtk_widget_modify_base (w1, GTK_STATE_NORMAL, (bFlipFlop)? &rgbEnd : 
&rgbStart);
gtk_widget_modify_base (w1, GTK_STATE_ACTIVE, (bFlipFlop)? &rgbEnd : 
&rgbStart);
*/

//modify relief style
gtk_button_set_relief(button, (bFlipFlop)? 
GTK_RELIEF_NORMAL:GTK_RELIEF_NONE);

//modify stock icon
gtk_tool_button_set_stock_id(GTK_TOOL_BUTTON(tool_pause), (bFlipFlop)? 
GTK_STOCK_MEDIA_PAUSE : GTK_STOCK_MEDIA_RECORD);

gtk_tool_item_toolbar_reconfigured (GTK_TOOL_ITEM(tool_pause));

return TRUE;
}

Why doesn't any of these work ? Any tips ?