fadeIn(color, duration = 1000, onComplete) {
		this._fadeIn.color = colorPool.get(color);
		const _alpha = this._fadeIn.color.alpha;
		this._fadeIn.color.alpha = 0.0;
		this._fadeIn.tween = tweenPool
			.get(this._fadeIn.color)
			.to({ alpha: _alpha }, { duration })
			.onComplete(onComplete || null);
		this._fadeIn.tween.isPersistent = true;
		this._fadeIn.tween.start();
	}
fadeIn effect <p>
fade to the specified color
@param {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);