Ok, this is a good topic of discussion, we know that these tubes were made of steel, stainless maybe, we know that these devices constantly toward keeping them, because they slipped inside another cylinder. This support consisted of oil or grease for better glide. However, the steel over time and with the constant humidity, usually change their tone, but as these tubes were constantly greased metal did not suffer so much aging.
Everything I say this because I think one of the most important parts, if not the most inportante was the periscope, this appliance could never fail and that is why they were doing constant maintenance.
As for color, unfortunately we do not have a color photo of the time, which tells us they were white, gold or silver.
We rely on photos of museums, where these pieces have been recovered somewhat in good condition and of course they clean all the waste and fat since they are exposed to the public.
These photos show two tubes of periscopes, in it we see a steel gold color and the other with a white color, the latter according to the photographer belongs to U_505 and what I can see, is the attack periscope ...
Again I apologize for my poor English, I hope I explained well
