An obscure but not so uncommon reaction from Sterling Silver, will be an a green-like stain on your finger that can appear in the first few days of wear.

There's two explanations for this;

Liver Of Sulphur

This is the perspiration from your finger, reacting with the blackening solution used in the detailed areas of the ring. We use a Liver Of Sulphur solution to darken the groves/details in the ring and with certain skin types, this may leak a small portion of the solution and give a green look on your finger. With most of our ring designs, the wide surface also creates a larger area for perspiration that will affect the 'green finger'. 
This is purely an early stage event. After a few times wearing the ring, this will stop! If not, just send us the piece back and we can give the ring a clean to rid the surface of any impurities.

Initial Base Metal Reaction

The second reason for this is just a direct reaction with a layer of base metal in the sterling silver. 

Let me explain; when you 'alloy' a metal like Sterling Silver (pure silver and base metals), it doesn't actually combine as such, it levels out in the alloy in layers. Therefore, simply how the alloy has formed, it may have a base metal layer right at the surface, which is in direct contact with your skin initially, causing the Green Tarnish stain early only.

Once again, this will subside after a few days, otherwise we can give your piece a quick polish to buff this away.