There were two different greens pre flag...Mint Green and a darker shade that I can't think of the name. I bought a gross box of the darker green long ago and still use it. It works as good as the preflag blue. I don't think it stains the cue shaft nearly as much as the blue...it's still there but lighter than the blue so it doesn't show as much. I have Tournament Blue cloth on my home table and you can't see any marks at all...unless someone else brings in some blue. And it doesn't show on the standard Forest Green either.
At this point, I prefer the green. Nobody else likes to use it so they don't even pick it up. I normally hold it all the time and when there is no chalk on the table and I offer mine to my opponent, they usually turn it down...their loss.
It comes in handy when somebody tries to accuse me of hording the chalk on the table because you never see green chalk used anywhere.
If you have the chance to get some green preflag, don't worry about anything. It's good stuff as far as my experience tells me.
JMHO...Ken