title: Flex 4.5 - Transparent Background on Spark DataGrid Headers
body: <p>In short, I am attempting to get this result:</p>
  
  <p><img src="https://i.stack.imgur.com/8wEtr.png" alt="Spark DataGrid"></p>
  
  <p>I almost got it, but the part that's giving me trouble is making the header background transparent. I am making a custom MXML skin based on the default Spark DataGrid skin. I tried setting the <code>contentBackgroundAlpha</code> to 0 on the columnHeaderGroup and the headerRenderer, but that didn't work. I tried setting <code>visible</code> to false for either of those, but that made it so that the text didn't show up either, so that didn't work. There is no setting for <code>backgroundAlpha</code> in either of those two, so I'm not sure what else to try.</p>
  
  <p>Any help would be greatly appreciated. Thanks!</p>