A really bad disco, or ????

[zygoma]

Honest folks, I tried. I even watched Das Boot again (still don't speak German, no subtitles, etc.) and am still stumped.
The Type VIIB I'm currently driving in the English Channel enroute to my patrol area has white overhead lights that are on sometimes. At other times their red counterparts are illuminated. I haven't found a pattern; does it have to do with whether the boat's on the surface (so Bernard can open the aft loading hatch to pee over the gunwales), or when the diesels are running, or ???
To further complicate my meager grasp, in the movie there are also blue lights that seem to be on quite often. At at least one time during the movie (the second attack on the sub?) the red and blue lights are alternating.
I noticed the conning tower has red and white lights in the sim, but didn't notice in the movie.
Also -- what are the porcelain-looking round devices in the panel in the forward overhead of the control room? In the VIIB they're immediately above the single battery charge state meter by the Chief Engineer's station; in the IID they're on the starboard bulkhead, forward of the dive plane stations, and above what looks like either a water distiller or an oddly-placed compressor.
In the movie, during one of the attacks, several of the shells of the devices appear to be broken (they look like cones screwed into a panel that also has either switches or rheostats on it). Fuses come to mind, although having them so far from the batteries leaves an awfully long supply line that can short and cause a fire or battery explosion, if the lead between the voltage source and the fuse shorts due to damage.
And having more than one fuse in line to a load can sure lengthen the troubleshooting procedure if one blows and the other doesn't.
Perhaps I'm overthinking this, although that's an offense I'm *very* rarely charged with -- usually I'm dinged for not thinking at all

So, any (printable) ideas?
Thanks yet again,
-- Zygoma --