So, I've been doing research about German WWII-era Uboats, and of course the subject of red lights come up and how they are used to better night vision and all the science behind that.
However, do we have any first-hand account proof that those Uboats actually had red lights? We can easily find proof of the red goggles that existed for such a use, but I can't seem to find any verifying the existence of red lights on the Uboats.

Thanks