Clever coloring! This looks exactly like oxidizing copper. The coloring on the dress is gorgeous, and I love the use of the butterflies and the beading of her shoulder straps. Really gorgeous work. :) I didn't realize that something as humble and simple as a penny could be turned into such a beautiful design!
I know exactly the color you're talking about and you've captured it well! The library in my town is partially made with copper and the metal is just starting to darken and turn :)
