"assisting the PIC with all those things which require colour vision when flying IFR."
Can anybody come up with a list of things which require colour vision when flying IFR?
I am talking of the relatively high standard of colour vision which one needs to see the patterns on the isihara plates, or (failing that) to see the tiny distant lights on the CAA lantern test.
The vast majority of people (men usually) who fail the above tests can distinguish all the normal colours perfectly, if presented in a realistic scenario, and in IMC this means instrument lights.