I used to have one as well. This was about 2 1/2 years ago. There are a couple of explanations. First it could have been an anvil created using ranger green ingots. Yes, that is a bit far fetched but slightly possible. Second, it could be a verite anvil and your screen color is off. I have an anvil that is the same color as frost wood but I have had it since before colored woods came out so the third possibility is that it is an old item that was accidentally (or not so accidentally) dyed.