Thank you for your Ask Jane question and welcome to the Be Jane community! In painting resin there is typically not a problem. The first question that comes to mind is, "Is it smooth surface or is it more textured?" If it is smooth or shiny you will have lightly sand it with nothing greater than a fine grade sand paper. This will add to the adhesion so that the paint will be able to stick better. Once you have finished sanding, you can go ahead and spray your frames with a spray paint made for plastic. One paint we've used is fusion paint from Krylon made for use on plastic. Just remember to tape around the edges of the mirror and cover the rest so you don't end up having to scrape it off the rest with a razor blade. We hope this helps. Let us know how this comes out.