but of course - perhaps he should have included some pix of these varieties in the flesh.

My copy is presently dismantled completely - am finally getting around to re-binding and making two volumes - so I can read it in the bath. It's the biggest single volume of all that I have, and it's tedious keep humping the lump on and off the shelf.
As regards these three varieties of Gay Glass (bet they wouldn't call it that now) - the 'Sunshine' amber seems not uncommon, with 'Spring' probably beating 'Evergreen' into second place - but that's just my experience - and I bet the Nile doesn't look remotely as green as this 'Spring'

Outside of Gay Glass, the bog standard amber - mostly in Bull's Eye pattern - has possibly been the most frequent of colours.
I've yet to find a piece of 'Cut Water Lily' - so am thinking this is uncommon - but more or less so than Webb's 'blue' I don't know.