Consider the sofa as a neutral. The best way to set a color palette is to have an inspiration piece. That piece is usually a rug or piece of art. Those colors are then used in pillows and decor. So find that piece first and everything else will follow.

If you are aiming for cozy, you can also consider adding a throw - lighter during the warmer months, heavier during the winter months. Rugs can also up the cozy factor. There are fabulous hooked rugs these days that run the gamut from country cozy to more contemporary. They usually aren't that expensive either. If you are into antiques, you can also find great vintage hooked rugs on eBay.

Would love to see what colors you use for pillows etc

i think the reversible sofa cover would come in hardy the
original sofa shield reversible furniture protector