I think the way we test for colour vision in aviation is somewhat arbitrary. I wonder what similarities there are between passing the Ishihara test or Nagel anomaloscope or this lantern test, or that - and flying the aircraft safely?
I've also often wondered how important 'normal' colour vision is in the flying task these days, especially when we're mostly IFR and have at least two radios?
It seems to me that p'raps a 'cockpit specific' test should be done (and failed) before anyone is ruled 'colour unfit/unsafe'?