I've seen it - a single plant may have both red and green stems; sometimes younger stems are one color or the other (can't remember which); also, a particular cultivar of rhubarb may have green stems rather than red stems.
Take a look at the following attachment...

Here is a link that might be useful: rhubarb petiole (stalk) color

Thanks AB - never heard of green only rhubarb - that must be what I have. The link gave good info and when it mentioned heavy seed head production that described my rhubarb all right. I thought it would be too tart and acidic to use but will cook up a batch and see what it tastes like.

We have a green cultivar. Made a pie last week and it was great. Rumor from the local Amish is that green rhubarb is tarter, so I added plenty of sugar. Used the recipe on the back of the tapioca box and added a tiny bit of cinnamon and orange peel.

I have purchased green rhubarb,and it tastes just fine cooked. I believe I added red food coloring to make it look pretty.

I have just returned from Rhubarbinfo.com its a site with all of your rhubarb varieties and questions, my understanding is that green rhubarb pending on what species can be sweet, check out the site rhubarbinfo.com

I love rhubarb, and when we first got our house I found a local farmer who was growing three different varieties, none of whose names he knew, two red and one green. DH and I tasted all three, and we both liked the green variety best. I wouldn't know how to rate it in terms of sweetness, but what I would say is that it had more of that characteristic rhubarby flavor, tangy and acidic. Well, now we have our own plants, they're huge and thriving, the stalks are giant, and I couldn't be happier! (I made three pies this week...) The red might look prettier, but I don't care.

That reminds me, I have to go and cut mine before it goes to head. Comopany coming, maybe rhubarb pie for dessert.

Some of mine are green, but most are red.

You could add some strawberries in to pink up your pies!!

I have red and green varieties, do not notice much difference in taste. I sometimes mix them in a pie. We have found the green variety much hardier and larger here.