The first version is based on the original mithril shirt scene from Fellowship. The second has a Rivendell exterior landscape in the background, as requested by an American lady in 2007.
I’ve included two detail pictures of Bilbo’s hands holding the shirt because the shirts are quite different. There was no opalescent or iridescent paint used in the silver area: just white, Payne’s grey, blue, green, crimson, and maybe some black as well? I think the gold part of the shirt in the second version did have a touch of actual shimmery gold paint. (It’s been a long time since I last looked at these scans.)