[Sailor Steve]

Just to add to what's been said:

All ships "rig for red" at night, not just subs. On-duty crew sometimes need to be inside one moment and outside the next. Red lighting keeps your eyes adjusted to the dark.

Blue lights have been a much-discussed subject, and there has yet to be an answer. I don't recall them being mentioned in the book, and I do remember somebody claiming Wolfgang Petersen said he did it just because it looked cool. I don't know that that's true; just repeating what I think I remember. I also don't recall ever hearing of any navy's ships using blue lighting for any reason, but I'll be glad to be corrected on that.