Final answer:
The Statue of Liberty's green color is due to the copper material used in its construction, which underwent oxidation-reduction reactions over time, forming a protective blue-green patina.
Step-by-step explanation:
The Statue of Liberty is green because of the copper, a reddish-orange metal used in its construction. When the statue was first delivered from France, it was brown due to the color of its copper 'skin'. The iconic blue-green color visible today is the result of a series of oxidation-reduction reactions that the copper underwent over time. Copper metal reacts with oxygen in the air, initially forming copper(I) oxide, which is red, then copper(II) oxide, which is black, and eventually producing a mixture of copper carbonate, copper hydroxide, and copper sulfate. These three compounds are responsible for the blue-green patina that acts as a protective layer against further corrosion, a process called passivation.