I took this photo on Montague and Clinton Streets in Brooklyn Heights, where a quartet of old-style subway entrance lamps have been preserved (or, as I suspect, made new to match the old styles). At one time all subway staircase entrances carried lamps like this, with the BMT (Brooklyn-Manhattan Transit) marked with green and Interborough Rapid Transit (IRT) marked with dark blue. I was shooting for the ForgottenBook and was using black and white film.
In the 1980s, remaining lamps of this type were re-fitted with red or green globes or half-globes. Green meant the entrance was open 24/7, while red meant it was closed part of the time, as of the 1990s, you could get in with a MetroCard.
At first, there were also yellow lamps, which indicated you could get in part of the time, but after the rise of the MetroCard they were dropped.