I have never seen completely green....now Grandma's was greener that the newer reds, but had some red. Does it taste like rhubarb.

I said I wouldn't kill any more rhubarb plants, but succumbed to a beauty at a feed store and bought another one.
I think it is the oldtimer Chipman's Canada Red.

Yes. It's fine. Simply a different variety of rhubarb where the stems will never turn red. Go for it.

Here is a link that might be useful: On Green Rhubarb