Yes, this changes the color of the screen. Not sure what you mean by "MB". Night mode makes the screen much darker and makes the scene look like night time (dark sky, darker ground and different colors for the roads); this makes the screen much less harsh (easier on night time eyes). However, one of the settings will prevent the night mode from activating. I think if you have traffic notifications turned on the night mode will not activate (this is one of the BMW things that makes no sense to me).

I live in a very rural area where traffic is not an issue so I leave this feature off. If I go into metro areas, where I might be concerned about traffic, I turn it back on. So I have button #1 programmed to toggle day/night. My Infiniti did this automatically with the automatic headlight sensor. If I were living in a urban area and wanted both night mode and traffic mode, I would use two "radio" buttons - one for toggling day/night and another for toggling traffic on/off (to permit the night mode to activate). Why BMW doesn't have automatic day/night mode activation with the headlight sensor is another BMW nonsensical decision (IMHO).