<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical" 
        verticalAlign="middle" 
        backgroundColor="white">

    <mx:Style>
        Accordion {
            selectedFillColors: haloBlue, haloBlue;
        }
    </mx:Style>

    <mx:Accordion width="400" height="120">
        <mx:VBox id="child1" label="Child 1" />
        <mx:VBox id="child2" label="Child 2" />
        <mx:VBox id="child3" label="Child 3" />
    </mx:Accordion>
    
</mx:Application>