Physical colored inks and coatings

A coating, such as ink or paint, is used, where particles in the coating are selected based on electric, magnetic, or light/photo properties, and are dispersed in the coating to provide a desired physical color. In one approach, the application of the coating to the substrate such as paper is controlled using an electric or magnetic field. In another approach, a pattern is formed in a coating on a substrate by targeting an electric, magnetic or photo field to specific locations on the coating. In yet another approach, the color of a coating that is applied to an object is shifted to match a background color so that the coating appears to be erased. In this approach, the coating may be in the form of a label, such as a bar code, that can be read by a scanner at a point of sale location. In another approach a pattern or code is scrambled or removed by applying an electric, magnetic, or photo field to specific locations on the coating or substrate.