Cover the spilled nail polish with a paper towel to absorb nail polish that has not yet seeped into the fibers of the seat cushions. Toss the soiled paper towel in the trash.
Test an acetone-based nail polish remover on the underside of the seat cushion. If it does not harm or discolor the fabric, drip some over the nail polish stain. Blot with a fresh paper towel from the outside in.
Note: If the acetone-based nail polish remover does damage the seat cushion fabric, use a nail polish remover without acetone instead.
Pour a dry cleaning solvent onto a clean white rag. Dab over any nail polish that remains on your seat cushions. Blot the liquid and stain up with a dry white rag.
Distribute a cap full of hydrogen peroxide over any traces of nail polish still visible on the seat cushion fabric. Wait two minutes and blot up with a dry white rag.
Flush the area of the seat cushions previously stained with cold water if they are not machine washable. Run the cushions through the washer if they are. Set in the sun to dry.