A mate of mine had a good one on one conversation with Dr Liddell at a safety seminar back in about 1996 or 97 where he advised that his restriction to day pvt VFR would now be lifted. As he recalls at the time, the Dr said something like the main reason they were restricting colour defective pilots from gaining ATPL was the concern of becoming visual close to the MDA / DA and having to transition straight onto the PAPIs.
The pilot has no trouble picking up the PAPIs at 5NM by day or night and has even done so with an FOI on board who was unaware of his condition.