What makes glass green that isnt in recycled glass?

I had two glass bottles of Coca Cola® with my lunch today, one was made of glass with a green tint and the other of clear, both bottles had the same batch number but from the markings on them i deduced that the clear one was made from recycled glass. The embossing on it was also not as legible as on the green bottle. What is it that is added to new glass to give it this green tint, what is the purpose of it and why is it lost when the glass is melted and re-moulded?