Answer by Yanger_xy

The problem is here: GUI.color.a = Mathf.Lerp(0.0f, 1.0f, (Time.time / 2)); You can not set GUI.color value seperately, you should set its value like this: GUI.color = new Color(GUI.color.r, GUI.color.g, GUI.color.b, 0) GUI.color = Mathf.Lerp(GUI.color, new Color(GUI.color.r, GUI.color.g, GUI.color.b, 1), (Time.time/2));