"At the Statue's unveiling, in 1886, it was brown, like a penny. By 1906, oxidation had covered it in a green patina."

This is from the article "Our Local Correspondents: Patina" by Ian Frazier, in The New Yorker issue for September 19, 2016. It's an interesting read. Apparently some looked into the possibility of painting the thing at one time, before wiser heads prevailed!