I get mine at Michael's. Find the gold leaf supplies and this is hanging with that stuff. It is a gold or silver paint. Brush it on with a brush you are going to throw away. It dries fairly quickly. I want to try regular gold leaf as well. The gold leaf texture would show through as well.

You can use any color behind the decal. The decal is printed on a clear mailing label. When creating the decal, anything that is white will be transparent and the base color will show through.