Well, I was thinking grey or a muted green. But then I thought maybe you should be picking the sofa you like best - unless you rugs are particularly new and you don't want to replace them any time soon.
Anything will match the walls the problem comes in with the rugs. You may want to look at the other accessories in the room to match colors. Try to find a print that brings out the color details of the rug along with the other items in the room. The easiest way is to just go to a fabric store and find one that you like and seems to bring all the colors together. You don't need a large piece. Bring the sample or samples home and see which ones match best and you like the most. Then go shop for the sofa. If you can't find what you want pick out the sofa you find the most comfortable and make a slip cover for it from the fabric you liked.