The flashing lights that activate on a school bus when it stops to load or unload children are red.
In the United States and Canada, alternating red lamps signal that the bus is stopped for student boarding or leaving. Drivers approaching from either direction generally must stop and wait while the lights flash, although divided-highway rules vary by jurisdiction. The lights are intended to protect children crossing the road near the bus.
School buses commonly use a separate set of amber warning lights before stopping. Amber lights warn drivers that the bus is preparing to stop; they are not the same as the red loading-zone signal. The familiar folding stop arm usually extends at the same time as the red lamps.
Exact enforcement differs among states and provinces, especially on divided roads, but red is the standard answer for the loading or unloading signal. White lights are not the normal stop signal, and blue is generally associated with emergency vehicles rather than school-bus loading.