// GRAYSCALE AND IMAGE snippet

// "Bit" is the linkage ID of the bitmap in the Library
var colorMC : Sprite = new Bit();

// sendToGray takes 3 parameters width, height, and Sprite
addChild( sendToGray( 306, 176, colorMC ));

function sendToGray( w:int, h:int, drawItem:Sprite ) : Bitmap
{
	var myBitmapData : BitmapData = new BitmapData( w, h );
	myBitmapData.draw( drawItem );
	
	var bmp : Bitmap = new Bitmap( setGrayScale(myBitmapData) );
	
	return bmp;
}

function setGrayScale( obj:BitmapData ) : BitmapData
{
    var rLum : Number = 0.2225;
    var gLum : Number = 0.7169;
    var bLum : Number = 0.0606; 
    
    var matrix:Array = [ rLum, gLum, bLum, 0, 0,
                         rLum, gLum, bLum, 0, 0,
                         rLum, gLum, bLum, 0, 0,
                         0,    0,    0,    1, 0 ];
    
    var filter:ColorMatrixFilter = new ColorMatrixFilter( matrix );
    obj.applyFilter( obj, new Rectangle( 0,0,obj.width,obj.height ), new Point(0,0), filter );
    
    return obj;
}

With this snippet you can change your color image from the library to grayscale (or it can be augmented to use any other color transform)

Change Image from Color to Grayscale

ActionScript 3