.ui-widget-overlay {
   background: #AAA url(images/ui-bg_flat_0_aaaaaa_40x100.png) 50% 50% repeat-x;
   opacity: .30;
   filter: Alpha(Opacity=30);
}

.ui-widget-overlay
{
  opacity: .50 !important; /* Make sure to change both of these, as IE only sees the second one */
  filter: Alpha(Opacity=50) !important;

  background: rgb(50, 50, 50) !important; /* This will make it darker */
}

open : function(event, ui){
    $("body").css({
        overflow: 'hidden'
    });
    $(".ui-widget-overlay").css({
        background:"rgb(0, 0, 0)",
        opacity: ".50 !important",
        filter: "Alpha(Opacity=50)",
    });
},
beforeClose: function(event, ui) {
    $("body").css({ overflow: 'inherit' })
}