code: function (color, duration, onComplete) {
              this._fadeIn.color = me.pool.pull("me.Color").copy(color);
              var _alpha = this._fadeIn.color.alpha;
              this._fadeIn.color.alpha = 0.0;
              this._fadeIn.tween = me.pool.pull("me.Tween", this._fadeIn.color)
                  .to({ alpha: _alpha }, duration || 1000)
                  .onComplete(onComplete || null);
              this._fadeIn.tween.isPersistent = true;
              this._fadeIn.tween.start();
          }
docs: fadeIn effect <p>
  fade to the specified color
  @name fadeIn
  @memberOf me.Camera2d
  @function
  @param {me.Color|String} color a CSS color value
  @param {Number} [duration=1000] expressed in milliseconds
  @param {Function} [onComplete] callback once effect is over
  @example
  // flash the camera to white for 75ms
  me.game.viewport.fadeIn("#FFFFFF", 75);