I don't know if I'd call mine yellow-green or yellow...
I do know it came recently from a grower in Peru.
I know we love positive I.D.'s but I'd expect variability in a bulb being sold by multiple vendors for 60 years. I also wonder how much cultural practices (soil, light, water, nutrients, temperature) change the appearance of bloom? Say, a green eye to a yellow eye?
I know in garlic, you can divide the same type of garlic from the same source, and give them to 12 farmers across U.S and canada, and you'll wind up with 12 possibly different looking bulbs at the end of the growing season, whose DNA is all statistically the same.
We need to cut a Hipp up, disperse the pieces far and wide, and compare the blooming pictures!