<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2007/09/13/checking-whether-a-color-name-is-a-valid-color-in-flex-using-the-stylemanager-class/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white" viewSourceURL="srcview/index.html">

    <mx:Script>
        <![CDATA[
            import mx.styles.StyleManager;
            import mx.utils.StringUtil;

            private function button_click(evt:MouseEvent):void {
                /* Remove leading and trailing whitespace. */
                var str:String = StringUtil.trim(textInput.text);
                var isColor:Boolean = StyleManager.isColorName(str);

                /* If it is a valid color, set the background color
                   and remove the error string, if any. Else, set the
                   background color to the constant NOT_A_COLOR from
                   the StyleManager class and set the error string. */
                if (isColor) {
                    box.setStyle("backgroundColor", str);
                    textInput.errorString = "";
                } else {
                    box.setStyle("backgroundColor", StyleManager.NOT_A_COLOR);
                    textInput.errorString = "NOT A COLOR";
                }
            }
        ]]>
    </mx:Script>

    <mx:ApplicationControlBar dock="true">
        <mx:Label text="Color name:" />
        <mx:TextInput id="textInput" />
        <mx:Button label="isColorName()"
                fontFamily="_sans"
                click="button_click(event);" />
    </mx:ApplicationControlBar>

    <mx:Box id="box" width="100%" height="100%" />

</mx:Application>