I think it depends on the shade of green. If your carpet is really a dark shade of green, then a light or soft tone is the one best to match. You can try using white paint and add a few drops of green to achieve a very light green. Painting your walls beige is also good. Plus you can make it better when you have a semi-white trim. But don't forget that the colour should also match your furniture like for example your Knightsbridge bedroom furniture or any solid pine furniture.