in reply to Soup Nazi, here's what JAA Manual of Aviation Medicine, page 42, states:
"The Beyne's lantern (lanterne chromoptométrique de Beyne) presents the colours green, red, blue, white, and yellow-orange with an aperture size corresponding to a visual angle of 3 minutes of arc. Each colour is shown for one second. The examinee is placed in front of the lantern at a distance of 5 meters. No errors are accepted."
I was wondering how UK CAA will operate this apparatus, provided that it can display the white light source and provided that it can have up to 6 aperture sizes...
Cheers !