title: Set JQuery UI modal dialog overlay background color dynamically
body: <p>i want change the page packground color when the modal dialog loadui-widget-overlay and property <code>background-color</code><br>
  when i set it with css it Works fine</p>
  
  <pre><code>.ui-widget-overlay {
     background-color: white;
  }
  </code></pre>
  
  <p><a href="http://jsfiddle.net/bniya_dev/gqque/" rel="nofollow">demo-with css</a><br></p>
  
  <p>but i want change it dynamically Because i have some modal dialog and i want change it only One of them <br>i try use jquery but it not work</p>
  
  <pre><code>$('.ui-widget-overlay').css('background', 'white');
  </code></pre>
  
  <p><a href="http://jsfiddle.net/bniya_dev/dmGe5/" rel="nofollow">demo-with jquery</a></p>
  
  <p>why? </p>