Whether you paint your clay before you work with it or after it has dried is up to you. Tinting your clay beforehand saves you a painting step later, plus if you sand it, you will reveal the tint color rather than the white of an untinted clay. The amount of acrylic paint you add when tinting depends on how dark you want your paperclay to be.
I prefer to apply a layer of matte medium on dry paperclay prior to applying a stain or painting the surface because it makes the clay less absorbent.
STEP ONE: Put acrylic paint on top of paperclay and fold over. Be sure to wear disposable gloves to protect your hands from the paint.
STEP TWO: Knead well to color the clay.
STEP THREE: Tint the clay with acrylic paint before molding.
Clockwise from top left: painted with red acrylic paint and topped with white acrylic glaze; Teal drybrushed over a Red Oxide base; Burnt Umber sanded to reveal white clay; gold rub on red-painted, stamped paperclay; silver rub and salt applied over wet black paint for an aged metal look.