See previous saran wrap nails post on how to do this!
Tried out a new technique for these! I painted a coat of silver polish and let it dry completely. I then painted a full coat of purple on one nail, and then took a small, bunched up ball of saran wrap and dabbed at the purple, exposing some of the silver and giving it this marble effect. Repeat on each nail one at a time and finish with a clear top coat!