<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2007/08/31/creating-a-flex-datagrid-control-with-a-transparent-background/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            import mx.events.ColorPickerEvent;

            private function colorPicker_creationComplete(evt:Event):void {
                colorPicker.selectedColor = Application.application.getStyle("backgroundColor");
            }

            private function colorPicker_change(evt:ColorPickerEvent):void {
                Application.application.setStyle("backgroundColor", colorPicker.selectedColor);
            }
        ]]>
    </mx:Script>

    <mx:Array id="arr">
        <mx:Object label="User 1" data="1" />
        <mx:Object label="User 2" data="2" />
        <mx:Object label="User 3" data="3" />
        <mx:Object label="User 4" data="4" />
        <mx:Object label="User 5" data="5" />
        <mx:Object label="User 6" data="6" />
        <mx:Object label="User 7" data="7" />
        <mx:Object label="User 8" data="8" />
    </mx:Array>

    <mx:ApplicationControlBar dock="true">
        <mx:Label text="backgroundColor:" />
        <mx:ColorPicker id="colorPicker"
                creationComplete="colorPicker_creationComplete(event)"
                change="colorPicker_change(event)" />
    </mx:ApplicationControlBar>

    <mx:DataGrid id="dataGrid"
            backgroundAlpha="0.0"
            alternatingItemColors="{[]}"
            dataProvider="{arr}">
        <mx:columns>
            <mx:DataGridColumn dataField="label" />
            <mx:DataGridColumn dataField="data" />
        </mx:columns>
    </mx:DataGrid>

</mx:Application>