It is widely agreed that the best paints for polymer clay are Water-Based Acrylic Paints. But alcohol inks, mica powders, and oil paints get a fair shout, too.
Of all 4 options, acrylic paints are cheaper and easier to get. But unlike the rest, you might have to wait a couple of days before baking the painted raw clay.
With so many shades and colors, you can readily mix to create new colors when you want. Thankfully, the texture is pretty consistent, so it is easy to blend.
Unlike the others, the SEISSO Mica Powder Pigment is mica powder, not acrylic paint. So, you can apply it to polymer clay and bake without having to wait. This cuts the painting process time of your craft short.