M-book mode in minimizes the visual differences between the monitor and the connected MacBook series product. While the monitor is connected to your MacBook Pro / MacBook Air, switch to M-book mode which represents MacBook’s color matching and visual representation on your monitor. If you intend to use dual monitors (i.e. your monitor and the MacBook Pro / MacBook Air are connected), the M-book mode is particularly helpful for minimizing the visual differences between two displays.