<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/01/02/changing-the-fill-colors-of-a-buttonbar-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white" viewSourceURL="srcview/index.html">

    <mx:Style>
        .customButtonBarFillColors {
        }
    </mx:Style>

    <mx:Script>
        <![CDATA[
            private function init():void {
                var cssObj:CSSStyleDeclaration = StyleManager.getStyleDeclaration(".customButtonBarFillColors");
                cssObj.setStyle("fillColors", [0xFF0000, "haloOrange", "haloOrange", "#FF0000"]);
                cssObj.setStyle("fillAlphas", [1.0, 1.0, 0.2, 0.4]);
            }
        ]]>
    </mx:Script>

    <mx:ApplicationControlBar dock="true">
        <mx:Button id="button"
                label="set button styles"
                click="init();" />
    </mx:ApplicationControlBar>

    <mx:ButtonBar id="buttonBar"
            buttonStyleName="customButtonBarFillColors"
            themeColor="haloOrange">
        <mx:dataProvider>
            <mx:Array>
                <mx:String>One</mx:String>
                <mx:String>Two</mx:String>
                <mx:String>Three</mx:String>
            </mx:Array>
        </mx:dataProvider>
    </mx:ButtonBar>

</mx:Application>