Forgotten NY is a really fun website. I believe they host tours occasionally as well.
I do use the red/green bulb system. Especially around stations with multiple entrances like Columbus Circle, Union Square, Antlantic Ave, etc. When I’m drunk, it’s late at night and it’s raining or incredibly cold and I can see two subway stations that are equidistant from my position…it is nice to know which of those stations is open ALL THE TIME. How many times before learning this system did I choose one of the two entrances and walk over to it, only to discover that awful locked gate at the bottom of the stairs or the dreaded no-metrocard-or-token-taking-unmanned turnstile? Then not only did I waste my time and energy walking to the stupid closed entrance but I have to haul my butt all the way over to the other entrance. The half red and white bulbs mean that the entrance is open on Sundays (red bulbs aren’t open at all on Sundays) but only at certain times. When in doubt, go to the green bulb even if it is further away.
As for those orange and green lights on the platforms… I’ve seen transit workers take them down and use them for illumination on the tracks. Whether this is their actual use is debatable, but I have seen them used in this fashion.