PURPOSE: To provide a color tone which varies when viewed from a different direction to a molding and also to provide a cubic impression to the color by coating the surfaces of a base material with optical interference films, reducing the above base material into powder or small pieces, and adding the resulting powder or small pieces to a molding material.

CONSTITUTION: An interference film 2 is formed on the surface of a base material 1 made of mica, etc., by successively laminating a high-refraction film 3 of TiO2, etc., a low-refraction film 4 of SiO2, etc., and a high-refraction film 5 of TiO2, etc., on the above surface. The interference film 2 is also formed on the opposite surface of the base material 1 in a similar manner as above. This base material 1 is cut and further cleaved into a state of powder or small pieces. The resulting powder or small pieces are used as an additive for molding plastics and added to a transparent casting resin, and the resulting mixture is molded. When the light from outside penetrates into the resulting molding and strikes on the additive, a green color, as an interference color, is allowed to appear in various color tones by means of the interference action of the light due to the interference films 2. Since the interference films 2 are scattered at various angles, the color can be allowed to appear in different color tones according to the angles of view.