Friends

The Farnsworth Lantern Test, or FALANT, is a test of color vision developed specifically to screen pilots for color blindness in the field of aviation.

 
One experience vividly illustrates the special impact of a lantern test.
A man came for examination, needing a certificate stating that his colour vision was adequate to pass a lantern test.
His wife sat with him in the darkened room, watching as he named the series of coloured lights presented. He misnamed red and green badly and I was unable to pass him.
They left but paused outside the door of the consulting room long enough for the lady to be heard saying, “Give me the car keys, I am driving home after that performance!”