Gradient Editor is a component you are probably familiar with from Flash, Photoshop, Fireworks. Unfortunately, there was no such prebuilt component included with Flex Builder. So here you go, i built one. Feel free to use it in your own projects.

You can add gradient colors by clicking on rectangular gradient area. To remove gradient color simply press slider thumb, move below component and release mouse.

View the app here(or click on a screenshot above).
View the source here
Download the source

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
    layout="absolute"
    xmlns:components="com.mariosh.components.*"
    backgroundColor="#FFFFFF"
    backgroundGradientAlphas="1,1"
    xmlns:local="*" viewSourceURL="srcview/index.html">

    <components:GradientEditor id="gEditor"
        width="200"
        height="50"
        x="32"
        y="40"
        colors="[0xff0000, 0x000000]"
        alphas="[.5, 1]"
        ratios="[100, 255]"/>
    <mx:HSlider
        minimum="0"
        maximum="1"
        change="gEditor.selectedAlpha=event.value"
        x="62"
        y="99"
        value="{gEditor.selectedAlpha}"/>
    <mx:ColorPicker id="cPicker"
        x="32"
        y="98"
        change="gEditor.selectedColor=cPicker.selectedColor"
        selectedColor="{gEditor.selectedColor}"/>
</mx:Application>