Код:
<?xml version="1.0"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml">
<mx:VBox backgroundColor="0xcc33ff" paddingBottom="10" paddingTop="10" paddingRight="10" paddingLeft="10">
<mx:VBox id="header" backgroundColor="0xcccccc" width="{component.width}" height="10" />
<mx:VBox id="component" width="400" height="200" backgroundColor="0x000000"></mx:VBox>
</mx:VBox>
</mx:Application>