It's a very simple technique. To colour an acrylic piece, normally I would use alcohol ink or paint markers. But to enhance embossed image on them, I would use solvent ink. Simply just rub your solvent ink pad (ie.Staz On) directly on the embossed image. If you want to have more colours on it, use a few paint markers (ie. Zig Painty) and doodle on them.