Light grey wall color is a perfect choice because it is so versatile. That means you can use just about any color you want for your seating area. I recommend solid navy blue for the seat cushion, with salmon and mustard toss pillows (you can also select pillows with patterns since the suggested seat base is solid). This color scheme matches your existing carpet.

I love silk but the sunlight will destroy it. Also, think dog and kids. Surely the loveliest but not the most practical. Yarn dyed would be better than painted or silk-screened or however they do the prints. Not only are dark colors going to fade faster they'll turn into completely different colors.

Try a solid Sunbrella zippered cover. Easy to wash. Add one or two solid Sunbrella pillows in colors from the rug.