A forklift blue light is a lamp that projects a bright blue spot onto the floor ahead of or behind a moving truck, to warn pedestrians that a forklift is approaching before it comes into view.
Blue lights became popular because a spot on the floor can show up around a rack end or at a doorway before the truck itself does, and because a projected light works in noisy areas where horns and alarms get lost. They are usually aimed a short distance behind the truck for reversing, ahead of it for forward travel, or both. OSHA 1910.178 does not require blue lights; fitting one is a site decision based on its own hazard assessment.
A blue light is a passive warning. It depends on pedestrians noticing the spot and knowing what it means, so training matters. It washes out in bright daylight and on light-coloured or reflective floors, it says nothing about whether the driver has seen the pedestrian, and when every truck has one the effect fades. It does not detect anyone. Blue lights belong in a layered plan alongside walkways, horns and, where risk is high, a detection system. The forklift blue lights guide covers where they help and where they fail.