If it's one thing (besides Jewelry) that I collect a lot of, it's magnets. I love them, don't you?
When working on hand stamped clay projects, I find that the best method for applying color is using pigment ink pads.
See the color on this? There are layers and layers of beautiful color on here, and this is achieved by using various shades of pigment ink, rather than acrylic paint.
When you're finished, you can spray it with a bit of acrylic sealer, though I opted not to. It's so pretty just as is, don't you think?