"Kill all uncessesary lights...."

[MarkQuinn]

Thank you both for your answers.

In addition, it is believed by some that play this game that the bright white lights are switched to red to indicate the time of sunset. This is partially true.

I'd watched a show about a modern US sub a long time ago (have since forgotten it) where the above explanation for the red lights was given: a sort of psychological effect for the crew so they do not feel they are living in perpetual daylight. The aspect of red light not traveling as far/being harder to spot also makes sense to me.

MQ