Thanks guys for the answers. Old TV Nut, your detailed response is very interesting in deed, certainly explains a lot.
One interesting thing I noticed with modern computer monitors is that when I've scanned a 12p emerald green UK queen head stamp on my scanner I don't get a matching emerald green, it looks like it has somewhat slightly more yellow in it, here's a couple of shots from a site of the stamp I'm talking about
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As you's notice they aren't as emerald as the actual stamp itself. I guess the phosphors you mention explain why a beautiful emerald green cannot really be achieved.
Just wondering though, the pure willemite P1 green phosphors, did it produce a nice emerald green colour to match that of a emerald 12p UK queen head stamp???