While most of us are limited to the visible spectrum, people with a condition called aphakia possess ultraviolet vision. Aphakia is the lack of a lens, due to surgical removal for cataracts or congenital defects.
A railroad lantern and a railroad lamp are two different things. Lanterns were designed to be portable (i.e. carried) and were basically globes surrounded by a metal frame with a fuel source. When you think of a railroad worker swinging a signal, think lantern.
Cab signals are presented to the locomotive by means of a cab signal display unit. The earliest CDUs consisted of miniature signals of the type visible along the track, back lit by light bulbs. These could be found in both color light and position light varieties depending on the railroad's native signaling system.