Lights inside U-boat...

[Enigma]

Red lights. regular white light etc....

Were this just to alert the crew to the "status" of the boat, or did they serve another purpose?

I know as a pilot, that red light is what you would use if you were using a flashlight in the cockpit at night, as it doesnt screw up your night adjusted vision when you look back outside of the aircraft.....perhaps this is another reason?