Set JQuery UI modal dialog overlay background color

That is in this css element:

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

it is on line 294 of: jquery-ui-1.8.11.custom.css


Add this CSS to your stylesheet:

.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 */
}

Easiest way is to use the themeroller.