Flex LineChart 动态添加线(LineSeries)及颜色

LineChart控件如何动态添加线，并设置线的颜色呢。找了很多资料都没合适的，不容易呀，下面直接上代码。

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
               xmlns:s="library://ns.adobe.com/flex/spark" 
               xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600" creationComplete="init()">
    <fx:Declarations>
        <!-- 将非可视元素（例如服务、值对象）放在此处 -->
        <mx:Stroke id = "s1" color="blue" weight="2"/> 
    </fx:Declarations>
    <s:layout>
        <s:VerticalLayout/>
    </s:layout>
    <fx:Script>
        <![CDATA[
            import mx.collections.ArrayCollection;
            import mx.charts.series.LineSeries;
            [Bindable]
            public var coll:ArrayCollection = new ArrayCollection([
                {Date:"2011-12-1",Value:2},
                {Date:"2011-12-2",Value:4},
                {Date:"2011-12-3",Value:5},
                {Date:"2011-12-4",Value:9},
                {Date:"2011-12-5",Value:6}
            ]);
            
            protected function init():void{
                var array:Array = new Array();   
                
                var lineSeries1:LineSeries=new LineSeries();  //设置图表的系列
                lineSeries1.xField="Date"
                lineSeries1.yField = "Value";
                lineSeries1.displayName="时间趋势图";
                lineSeries1.setStyle("form", "curve");  
                lineSeries1.setStyle("lineStroke",s1);
                array.push( lineSeries1 );
                myChart.series = array//给图表系列赋值
            }
        ]]>
    </fx:Script>
    <mx:Legend dataProvider="{myChart}" height="20"/>
    <mx:LineChart id="myChart"  dataProvider="{coll}"  width="400" height="360" showDataTips="true">
        <mx:verticalAxis>
            <mx:LinearAxis id="laxis" autoAdjust="true" baseAtZero="false"  />
        </mx:verticalAxis>
        <mx:horizontalAxis>
            <mx:CategoryAxis id="ca"
                             dataProvider="{coll}"
                             categoryField="Date"
                             />
            
        </mx:horizontalAxis>
        <mx:horizontalAxisRenderers>
            <mx:AxisRenderer axis="{ca}"
                             canDropLabels="true" />
        </mx:horizontalAxisRenderers>
        <mx:series>
        </mx:series>
    </mx:LineChart>
</s:Application>