An interesting read below regarding the B727 which crashed in Tallahassee in 2002. The FO's CVD was implicated as a possible causal factor and ever since many worldwide authorities continue to quote this accident as a justification for more stringent colour vision requirements.
The article raises some serious issues which must be examined and in particular questions the reliability of the PAPI to provide correct indications under certain atmospheric conditions:
The Puzzle of the Crash of FedEx Flight 1478: Implications for Colour Vision Standards in Aviation