Ease color transform, little help!

Hey! I’ve got this code to change the color of movieClip. Anyone got any idea, how to transform this prototype that it’s gonna EASE to another color? Searching for smooth effect.

Thank you very much!

MovieClip.prototype.tint = function(colour:Number):Void  {
 var tempColor:Color = new Color(this);

 tempColor.setTransform ({ rb:(colour >> 16) & 0xFF, gb:(colour >> 8) & 0xFF, bb:colour & 0xFF});


btn.onRollOver = function(){