Fig. 1: Difference between Indicator lamps (bottom) and a normal Lamp (top) emitting light.
The Indicator lamp is a block added by RedLogic. It requires a redstone signal to be turned on. In contrast to the standard Lamp or other light sources, the Indicator lamp does not emit light beyond itself (shown in Fig. 1)—in other words, it does not prevent hostile mobs from spawning. The Indicator lamp comes in 16 different colors.
