Can you identify these vintage Knoll chairs?  

Risom
Look like Risom.
Is the upholstery really that bad?

Looks like risom to me as...
Looks like risom to me as well.... especially the base. But I also wonder, why reupholster them if they are in great shape?

Well, one of the chairs has...
Well, one of the chairs has a big stain on it. Plus, the fabric is an unattractive green color. Thanks for the info, though!

I can see
The stain, but the other two look fine.
Puke green is all the rage. In all seriousness, you should not redo the upholstery if you want to maintain their value.

Perhaps you could get the...
Perhaps you could get the stain out? If you don't like the color, and they are in great shape ... sell them!!!! Make some good $$$$ and get something you want perhaps.

These are exactly what I...
These are exactly what I want, just not the right color. And their value isn't of much concern to me. Thanks for the suggestions, though.

Well then, save the oringal...
Well then, save the oringal fabric.
Make a square bag of fabric and place the original, cleaned fabric inside. Affix this to the underside of chairs.
Something to consider...

I am confused
by that statement, the chosen uno, that their value is of no concern to you.
Do you mean that the chairs just have the look, shape, height that you needed and their design history and all that entails is of no concern to you?
Or do you mean that their monetary value is of no concern to you because you would have bought them no matter what because they were manufactured by Knoll?
As both a buyer/collector and a seller, I am muddled and yet intrigued by your statement. Could you expound, if you don't mind?

So sorry,
forgot to add that the stain on the chair in the forefront is just a watermark, probably from a leak in a ceiling or roof. It should come out with just a gentle detergent (like dish soap and hot water) and scrubbing.

They look simple. COuld you...
They look simple. COuld you reupholster over the fabric so it could be changed back by a future buyer if you were to sell?

Happy to explain about my com...
Happy to explain about my comment. I bought them because I value their place in design history and because I think they're beautiful chairs. I bought them specifically for my loft because (once they're a different color) they'll go perfectly.
I tend to buy furniture (and art, for that matter) because I like it - both aesthetically and historically. I don't buy furniture with the hope of one day reselling it at a profit, just like I don't buy art to resell it. The furniture and the art I have amassed over the years are, I think , absolutely beautiful and make my home truly unique. I bought it all for the present - that is, my enjoyment - and not for the benefit of my estate.
Some may disagree, but that's my take on art and furniture.

Nothing wrong with that...
But what happens when your aesthetic / tastes change?

To your point, then, I wholeh...
To your point, then, I wholeheartedly agree. I once had a vintage Eames sofa in snot green, and recovered it for my pleasure. I do have to say, though, eventually I ended up growing rather fond of that color and wished I had left it. But if you feel that won't happen by all means they're yours. Have fun!
I tend to buy what I like too, paying no attention to value.

And while we're on teh...
And while we're on teh subject, I have recently found an excellent source for Knoll, Herman Miller, Maharam fabrics and more at a great price. These people buy excess and leftovers from other dealers and resell at amazingly low prices. Some KNoll fabrics are as low as 12 bucks a yard!!!! Plus you can feel good that the scraps don't end up in the dump...
http://www.modern-fabrics.com