no it's not an bug in the drawadd, what you are trying to do should be done as following:
Code:
    GLXDraw1.UseColor(1.0, 1.0, 1.0, 0.2);
    GLXImageList1.Items.Find('Wood.jpg').Draw(20,20, 0);
    GLXDraw1.UseColor(1.0, 1.0, 1.0, 1.0);