ctor(duration, colorFromWhite, colorFromMid, colorFromBlack, colorToWhite, colorToMid, colorToBlack) {
    cc.ActionInterval.prototype.ctor.call(this);
    this.initWithDuration(duration, colorFromWhite, colorFromMid, colorFromBlack, colorToWhite, colorToMid, colorToBlack);
  }
Animates the screen space gradient color map.
NOTE: only run this action on the scene, as it affects global state and the scene is the only guaranteed persistent node.
@function
@param {Number} duration
@param {Color}  colorFromWhite
@param {Color}  colorFromMid
@param {Color}  colorFromBlack
@param {Color}  colorToWhite
@param {Color}  colorToMid
@param {Color}  colorToBlack