Changing color of GtkRadioButton

[Edoardo Vigoni <vigoni aero polimi it>]

How can I change color of GtkRadioButton when it's pressed? Usually it
has the same color of the window background and it isn't so clear. I can
do it with GtkCheckButton, but I can't with RadioButton. How can I do?
For CheckButton I do in this way:

void set_color_check_button(GtkWidget *Widget)
{
GdkColor        Color;
GdkColormap     *Cmap;
GtkStyle        *Style;

        Style = gtk_style_new();
        Cmap = gdk_colormap_get_system();

        gdk_color_parse("dark red", &Color);

        if (!gdk_color_alloc(Cmap, &Color)) {
                g_error("couldn't allocate colour");
         }

        Style -> bg[Widget->state] = Color;

        gdk_color_parse("pale green", &Color);

        if (!gdk_color_alloc(Cmap, &Color)) {
                g_error("couldn't allocate colour");
        }

        Style -> bg[GTK_STATE_ACTIVE] = Color;
        gtk_widget_set_style(Widget, Style);
}


Thanks for your time
Edoardo