Here's a good question: when, where and how would you use lanterns with blue, green, red, and whatever colour globes?

BLUE is universally linked to Rule 26, INSPECTION AND REPAIR PROTECTION.

RED used to be a flagman's lantern, until red fusees replaced them because they are brighter.

YELLOW used to be used to modify the red STOP aspect of a two color train order signal to the more permissive "19" aspect (pick up orders on the fly).

I'm not sure about green under traditional railroad rules, but when I worked on the Chicago elevated during the seventies, red and green lanterns together defined a temporary SLOW ZONE, and a single green lantern was the release at the end of the slow zone.

http://www.railroadiana.org/globes/pgGlobes.php

seems there can be widely varied rules per railroad, the use is flag by day, light by night. Seems useable where a standard signal is not located. I presume you could hang a red lantern at the end of a train that may be cabooseless for whatever reason.

Green and White lanterns placed together were a stop indication for a flag stop. Red would also be used to mark the end of the train in cases where markers could not be used or were inoperable. A white light was also used to mark the front of a train in a scenario where the locomotive was pushing from behind. I say "mark" because it sure couldn't illuminate the right of way at night. On more than one occasion where a marker lamp had gone out, I wired the handle of my red lantern to the gate of the rear passenger car.