Don't panic, the ring is solid sterling silver (92.5% Silver).  This "green finger effect" is a reaction between the acidity content of your sweat with an alloy in the sterling silver.  It happens to about 1 in 60 people.  Most retail jewelry is industrial plated with rhodium (rhodium is in the same metals family as platinum), which prevents this reaction from happening.  We do not industrial plate all of our rings.  

If your are having this reaction, we are happy to plate your ring for free with rhodium.  Just send the ring back with a copy of your sales receipt and a note that you need the ring rhodium plated.  NOTE:  We suggest insuring the package for the value of the ring.  We will not replace or refund rings lost or stolen in the mail while in delivery from you to us.

Another solution is to simply clean the ring every day with a silver polishing cloth.  They can be found at local jewelry stores or department store jewelry counters.  After about a week or two, the reaction will stop occurring.