greyscale a movieclip

myMovie.filters = [ new ColorMatrixFilter(getSaturationMatrix(0) ]

private function getSaturationMatrix(value:Number):Array {
   
    var nRed:Number = 0.3086; 
    var nGreen:Number = 0.6094;
    var nBlue:Number = 0.0820;
    var nA:Number = (1 - value) * nRed + value;
    var nB:Number = (1 - value) * nGreen; 
    var nC:Number = (1 - value) * nBlue;
    var nD:Number = (1 - value) * nRed;
    var nE:Number = (1 - value) * nGreen + value;
    var nF:Number = (1 - value) * nBlue;
    var nG:Number = (1 - value) * nRed;
    var nH:Number = (1 - value) * nGreen;
    var nI:Number = (1 - value) * nBlue + value;
   
    return [nA, nB, nC, 0, 0, nD, nE, nF, 0, 0, nG, nH, nI, 0, 0, 0, 0, 0, 1, 0];
}

To turn off the greyscale:

myMovie.filters = [ ]