Actually, I don't know that it would necessarily have to be epoxy... there seem to be other versions, as well.
http://www.google.com/#hl=en&q=clear+casting+resin
I've seen some of these (Castin' Craft and Easy Cast) at my local craft stores, and I've also seen the dyes for them. One of the stores had a sample cast tinted with a light green and, other than being full of bubbles, it was pretty clear, and seemed like it might work.
http://www.google.com/#hl=en&q=clear+casting+resin
I've seen some of these (Castin' Craft and Easy Cast) at my local craft stores, and I've also seen the dyes for them. One of the stores had a sample cast tinted with a light green and, other than being full of bubbles, it was pretty clear, and seemed like it might work.