Unable to make a color change

[MC_Vai <estoy ver megared net mx>]

        As a disclaimer I did read
        http://www106.pair.com/rhp/gtk-colors.html

        But still I haven't been able to change the color of
        a GtkLabel's background.
        Here is my code:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/* file1.c */
GtkWidget       *eb, *label;

eb = gtk_event_box_new();
...
label = gtk_label_new( whatever );
...
gtk_container_add( GTK_CONTAINER(eb), label );
...
set_display_style( label->parent, label );

/* file2.c */
void
set_display_style( GtkWidget    *bgwidget,
                   GtkWidget    *label )
{
        GtkRcStyle      *display_rcstyle;
        GdkColor        black_color;
        GdkColormap     *colormap;

        colormap = gdk_window_get_colormap( win );
        gdk_colormap_ref( colormap );
        black_color.red = black_color.green = black_color.blue = 0;
        gdk_color_alloc( colormap, &black_color );
        gtk_colormap_unref( colormap );

        display_rcstyle = gtk_rc_style_new();
        display_rcstyle->bg[GTK_STATE_NORMAL] = black_color;
        display_rcstyle->color_flags[GTK_STATE_NORMAL] |= GTK_RC_BG;

        gtk_widget_modify_style( bgwidget, display_rcstyle );
        gtk_rc_style_unref( display_rcstyle );
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

        But is not working... (the color shown is the same of my
        desktop's theme).
        Is there something I'm missing?

        Thanks a lot in advance for your help.
        Regards,

                                             - Eduardo.