What color is the outer marker in an ILS implementation?

The outer marker in an Instrument Landing System (ILS) implementation is blue. The outer marker serves as a key reference point for pilots, indicating the location where the aircraft is approximately 4 to 7 miles from the runway threshold, typically aligned with the final approach course. Its blue color is standardized to differentiate it from other navigational aids, such as the middle and inner markers, which are indicated by different colors. Understanding the color coding of these markers is crucial for pilots during approaches, as it helps in situational awareness, particularly in low-visibility conditions. The blue color provides a clear, recognizable signal that assists in guiding the pilot during the approach and descent phases of flight.