For those of you who miss the ability from Silent Hunter II to switch to red light on command (day or night), I found a workaround you might want to try that should work for SH5, SH3 or any sub sim for that matter.
It's an application called ColorVeil which puts a color filter of your choice over your whole screen and can be assigned to a keyboard command. I was using it because staring at bright white spreadsheets all day hurts my eyes and then when I picked a red filter, it reminded me of the red light in subs.
I picked a burgundy red at 50% opacity, but you can play around with it and choose a color of your liking. I bound it to CTRL + F10 since that doesn't seem to be in use by SH5:
Here's what it looks like when I activated the filter in-game, during the daytime:
You can download the application here:
https://www.east-tec.com/colorveil/
Good hunting!