Inside the submarine, only two places use red light. One; the berthing and the other one is the control room. Under normal conditions, all the white lights are turned on to facilitate movement, alertness, and awareness of the crew. The same white lights are utilized even when the submarine is present on the surface, at the port, or even when it is submerged. So, questions arise that in which conditions the red lights replace the white ones, and why this happens. Here you will find the answers to these queries.
The idea that Red light diminishes the ability to see in the dark is a myth. In fact, the presence of red light helps in the adjustment of vision. Not only submarines, but airport control towers, planetarium, and some movie theaters also use red light so that it is easier for the viewer’s eyes to adjust from light to dark. The submarine crew needs to acclimate the eyes before going topside for the night watch. This vision adjustment is the primary reason for using the red lights.
One of the other reasons is to prevent light from being emitted from the raised periscope. Although the blackout blind covers the scope, yet, there is still a risk of light being emitted from the other end of the periscope. This light can be seen for miles and getting detected for a submarine could serve as havoc.
A stage light is also a wonderful option for a submarine because it is environmentally friendly and cheaper than other options. Also it is a lot better than traditional lightning options.
Source: The Aviationist
Can you think of some other reason why these red lights are used? Tell us through your comments!