If you get low on some approach light guidance systems they turn red - is this noticed by colour defective pilots?
4Greens - Have a look at the YouTube presentation I posted on page 1 of this thread regarding the Case Studies of Professional Pilots with a CVD.
You will see that between these 3 pilots, there has been a combined total of several thousand PAPI approaches flown. As one of these pilots, I can honestly say that PAPI has never posed an issue for me.
CVD pilots are required to pass the same high standards in flight and sim checks as colour normals. 23 years worth of evidence in Australia indicates we are just as capable of performing all required tasks with no difficulties.