understanding GtkRGBA

[Rudra Banerjee <bnrj rudra yahoo com>]

Dear friends,
though this might be Fedora(or gnome shell theme Adwaita) specific
problem, I cannot get color from:

GdkColor colorRed2 = {0x0000, 65535, 29555, 24158};
gtk_widget_modify_bg(button, GTK_STATE_NORMAL, &colorRed2);

So, I am trying to use:

gtk_widget_override_background_color (Hbutton, GTK_STATE_NORMAL,
GdkRGBA(0,0,0,1.));

ofcourse, this is not the way to use RGBA.
What is the correct way of using it?