Stable zircon pigment particles, at least about 50 percent by volume of which range from about 0.2 to about 2.5.mu. in size, provide useful heavy metal free pigments for plastics and paints. A method for coloring plastic and paint materials without the use of heavy metal pigments comprises the step of adding to the material, in an amount of 0.5 to about 10 percent by weight, stable zircon pigment particles, at least about 50 percent by volume of which range from about 0.2 to about 2.5.mu. in size.