What is the primary purpose of blue lights on an airfield?

The primary purpose of blue lights on an airfield is to identify taxiway edges. These lights are strategically placed along taxiways to provide pilots with visual guidance during taxiing operations, especially during low visibility conditions at night or in inclement weather. The blue color is specifically designated to indicate taxiway edges, ensuring that aircraft maintain a safe distance from areas not meant for taxiing or other operations.

While other colors and lights serve important functions, blue lights are uniquely associated with the edges of taxiways and help avoid potential accidents by clearly delineating where a taxiway begins and ends. This visual cue is crucial for pilots and ground personnel to navigate safely around the airfield.