The following example uses a Slider to select a number between 0×000000 (black) and 0xFFFFFF (white) to use for the background color of a box. We use the slider’s tool tip to display our nicely formatted number, although we could have used a Label or anything else just as easy.

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2007/07/25/formatting-colors-as-strings-with-actionscript/ -->
<mx:Application name="Color_format_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            private function intToHex(color:int = 0):String {
                var mask:String = "000000";
                var str:String = mask + color.toString(16).toUpperCase()
                return "#" + str.substr(str.length - 6);
            }
        ]]>
    </mx:Script>

    <mx:Box id="box"
            width="200"
            height="100"
            backgroundColor="{slider.value}" />

    <mx:HSlider id="slider"
            minimum="0x000000"
            maximum="0xFFFFFF"
            liveDragging="true"
            dataTipFormatFunction="intToHex"
            width="{box.width}" />

    <mx:Label text="{intToHex(slider.value)}" />

</mx:Application>

View source is enabled in the following example.

Although quite uninteresting, this code works by taking the color as a numeric value, converting it to a hexadecimal string using toString(16), converting that string to uppercase and prefixing six zeros in front of that string. Now, to make sure we only return a maximum of six alpha-numeric digits, we use the substr() method to just grab the end of the string. Pretty easy, huh?