I tell you what would kill the landing light problem stone dead for ever. The green lights (or when showing green)... stick a cheap, semi-circular dark blue filter over half of the green lamp, or a just wedge of coloured self-adhesive cellophane. to make a turquoisey blue. Then both the red-green area guys, and those with the very rare blue trouble would be proveably 100% fine. In fact a 120 degree filter would be enough.
In discussions years back, the idea of changing lamp colours was raised. The CAA didn't mention cost, but did say words to the effect that the instinctive perception and understanding of the meaning of red and green is so entrenched as to be unopen to question, which has some validity.
On a global or even country scale this would seem a huge undertaking, but in fact would be no more than a few quid per lamp. The bureaucracy, communication and attendant faffing is another matter.
It's very difficult to explain to many colour-normal people that in most situations, colour deficiency is not a problem. Glass cockpits are such a situation I believe, but that's a discussion for later... 'cos I am about to eat!