Flex ColumnChart获取得焦点改变颜色

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical" verticalAlign="middle" backgroundColor="white">
    <mx:Script>
        <![CDATA[
            import mx.charts.chartClasses.IAxis;
            private function linearAxis_labelFunc(item:Object, prevValue:Object, axis:IAxis):String {
                return numberFormatter.format(item);
            }
        ]]>
    </mx:Script>
    <mx:NumberFormatter id="numberFormatter" precision="3" />
    <mx:ArrayCollection id="arrColl">
        <mx:source>
            <mx:Array>
                <mx:Object name="R Winn" obp=".353" slg=".445" avg=".300" />
                <mx:Object name="P Feliz" obp=".290" slg=".418" avg=".253" />
                <mx:Object name="O Vizquel" obp=".305" slg=".316" avg=".246" />
                <mx:Object name="B Molina" obp=".298" slg=".433" avg=".276" />
                <mx:Object name="R Durham" obp=".295" slg=".343" avg=".218" />
            </mx:Array>
        </mx:source>
    </mx:ArrayCollection>
    <mx:ColumnChart id="columnChart"
            showDataTips="true"
             dataProvider="{arrColl}"
             selectionMode="single"
             itemRollOverColor="haloSilver"
             itemSelectionColor="haloBlue"
             width="100%"