A soft grey could be very nice. Bring soft palette accent colors in to move the eye around the room and create interest.

Blue could be very nice. Several shades could work.

http://houzz.com/photos/2200837

http://houzz.com/photos/12374957

A beige sofa could also work. Just be sure to stay away from yellow undertones as your brown carpet seems to have a gray undertone.

http://houzz.com/photos/2595757

I would get a taupe sofa, then select a lighter and brighter color to bring in - maybe yellow.

Blue with pillows that match the curtains

Firstly,do you like the carpet and can you live with it for the next 10 years? No point in buying furniture to match something you can not tolerate.
Having said that, I would chose a lighter gray-beige colour for your sofa, add some cushions and a chair in an accent colour and think about painting the walls.

Thanks everyone :)

What color would she paint the walls?

We just bought a house that also has dark carpet in the living room. I typed in "dark carpet" in the search window on houzz then narrowed the pictures down by clicking on "living room" on the left. I came across some good ideas for wall color & furniture color. Luckily, we have 2 club chairs in cream that go nicely. Good luck!