green and yellows are almost different species in their behaviour IMO...
The yellows are bold and aggressive, the greens are meek and usually the victim of aggression.
I have tried both, even together in my early days of reefing and admittably, tried a few of the 7 dollar fishes and always found the greens were dominated by the yellows.
I have never seen a green nip at polyps, but again, my current yellow one has never been seen eating anything BUT sps polyps.
Only my observations, no labratory scientist here....
