Flex 4怎么设置ComboBox内图标标记颜色

Flex 4如何设置ComboBox内图标标记颜色
<?xml version="1.0" encoding="utf-8"?>

<s:Application name="Halo_ComboBox_symbolColor_test"         xmlns:fx="http://ns.adobe.com/mxml/2009"         xmlns:s="library://ns.adobe.com/flex/spark"         xmlns:mx="library://ns.adobe.com/flex/halo">    

<mx:ApplicationControlBar width="100%" cornerRadius="0">         <mx:Form styleName="plain">            
<mx:FormItem label="symbolColor:">                
<mx:ColorPicker id="colorPicker" />             </mx:FormItem>        
</mx:Form>   
</mx:ApplicationControlBar>    
<mx:ComboBox id="comboBox"             dataProvider="[The,Quick,Brown,Fox,Jumps,Over,The,Lazy,Dog]"             symbolColor="{colorPicker.selectedColor}"             horizontalCenter="0" top="60" />
</s:Application>