Abaixo o exemplo de como realizar a alteração das cores de uma imagem:
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="horizontal" backgroundColor="white">
<mx:Script>
<![CDATA[
private var rLum:Number = 0.2225;
private var gLum:Number = 0.7169;
private var bLum:Number = 0.0606;
[Bindable]
private var bwMatrix:Array =
[rLum, gLum, bLum, 0, 0,
rLum, gLum, bLum, 0, 0,
rLum, gLum, bLum, 0, 0,
0, 0, 0, 1, 0];
[Bindable]
[Embed('assets/image2.jpg')]
private var image2:Class;
]]>
</mx:Script>
<mx:ColorMatrixFilter id="cmf" matrix="{bwMatrix}" />
<mx:VBox>
<mx:Label text="Black and white" />
<mx:Image source="{image2}" filters="{[cmf]}" scaleX="0.5" scaleY="0.5" />
</mx:VBox>
<mx:VBox>
<mx:Label text="Original" />
<mx:Image source="{image2}" scaleX="0.5" scaleY="0.5" />
</mx:VBox>
</mx:Application>
Fonte : http://blog.flexexamples.com/2007/07/27/converting-an-image-to-black-and-white-using-the-colormatrixfilter/