title: how to change background color of column header for AdvancedDataGrid control in flex
body: <p>I have below columnGroup in advancedDataGrid control and I want to show the header in red background color and also applied the style but the <strong>background color</strong> in the <strong>header</strong> does not show as red only the text color in the header is changed.</p>
  
  <pre><code> &lt;mx:AdvancedDataGridColumnGroup textAlign="center"  headerStyleName="myHeaderStyles" &gt;
  </code></pre>
  
  <p>....</p>
  
  <p>I also have the following style defined</p>
  
  <pre><code>&lt;mx:Style&gt;
     .myHeaderStyles {
          color: red;
          fontWeight: bold;
          background-color:red;
          background-disabled-color:red;
          area-fill:true;
  
      }
  
  &lt;/mx:Style&gt;
  </code></pre>