I have a plum color rug and the walls are off white. I need to buy 2

If your lifestyle allows, you could use off-white sofas with colorful throw pillows in plum printed accent fabrics.

Blue Green or Teal with Yellow Orange

or

Green with Yellow

or

Yellow Green

will work in your room.

My favorite would be a Brown couch that is more yellow than red with Teal throws, & throw pillows that contain Teal and Yellow Orange.

Gray would look great with combo and it’s nietral so you change your colors.

Do you have a monochrome theme or do you want contrasting colors?

Cream would also work and you could use cushions to bring different colours in, you might want to try this neutral colour in case you want to change the carpet to a more neutral pallet in future. It depends on your taste, of course, good luck with your purchase.

grey would look awesome!

I would choose gray as well. It coordinates beautifully with plum, and doesn't look dirty fast. It also goes well with many other colours. Over the years, I have regretted buying coloured sofas. Neutrals are best IMO.

I would go light gray myself, and I also like white but its harder to keep clean.

I would go with a "pearl" sort of pale gray or a light mocha color. Light neutrals, but not too cool so that everything, including you!, doesn't take on a gray cast in the room.

Just me, but I love sage green and plum, purple, lavender. Go to a sofa store and grab some sample swatches, bring them home and lay them on the rug. That will at least give you some idea of what color you should go with.