Definition
A reduced ability of the eye to distinguish certain colors, most commonly red and green, but in some cases blue and yellow. In aviation medical certification, color vision is tested because pilots must be able to correctly identify the colored lights used in airport signaling, navigation lights, and cockpit displays. A pilot with a color vision deficiency may receive a medical certificate with an operational limitation, or may be required to pass a practical signal light test before flying without restriction.
Plain English
Trouble telling certain colors apart, usually reds and greens. Because pilots rely on colored lights and signals, the FAA tests for this during the medical exam.
Context Anchor
Seen in aviation medical exams, medical certificate discussions, night operations, airport light-gun signals, cockpit displays, and color-coded charts or markings.
Derivation
Deficiency comes from a Latin idea meaning “to lack” or “to fall short.” That helps here because the term does not mean vision is absent; it means the ability to tell some colors apart falls short of the normal range.
Why Pilots Care
FAA rules require adequate color vision to safely read navigation lights, airport beacons, and instrument displays.
Intuition Check
Color vision deficiency does not always mean total color blindness. It usually means certain colors are harder to tell apart, and aviation focuses on whether the pilot can still identify safety-critical colors correctly.
Example Sentence 1
Because of his color vision deficiency, his medical certificate carried a limitation against night flying until he passed a signal light test.
Example Sentence 2
The pilot's mild color vision deficiency made it harder to separate the red and white lights on the approach path at dusk.