Remove Color Transform?

[SwirlyKing]

I made this function to color buttons as you click on them, but I need to be able to remove the color transform later. I tried:
this.btn1.transform.colorTransform = null;
but it says it can't be "null".

function colorBtn(c, b) {
    var colorTransform:ColorTransform = this["btn"+b].transform.colorTransform;
    colorTransform.color = c;
    this["btn"+b].transform.colorTransform = colorTransform;
} 

[neznein9]

try

= new ColorTransform();

[SwirlyKing]

that's it!
Pretty soon I'll get the hang of AS3. Thank you again.