Hi, in the type IXC there was no red lighting. Quoting the US Navy Evaluation found here [uboatarchive.net] "Low level illumination for dark adaptation is not provided. Control instruments have been treated with relatively long persistence phosphorescent material." I believe that the type VII was the same. In type VII Manual found here [uboatarchive.net] it says "The night lighting is powered from light groups and in the following rooms consists of:
Petty officers room, Officers and chief petty officers room, Forward torpedo room" Note the "night lighting" which I think is just dim lighting not red lighting is found in the living spaces and not in the control room or conning tower. There is no mention of any lighting for night adaptation. I believe that the watchstanders wore goggles to adapt before going onto the bridge. Probably at night the control room and conning tower were kept very dimm to avoid any light being visible from the open conning tower hatch. Jerry