1. A computer operable method of modifying half-toned pixel data for a selected pixel that contains black and does not contain a predetermined non-black primary color, the selected pixel being in a half-tone cell for the predetermined non-black primary color, comprising: determining at least one non-black primary color as the predetermined non-black primary color; selecting a pixel which contains black and does not contain the predetermined non-black primary color; obtaining half-toned data for any pixels in neighboring half-tone cells for the predetermined non-black primary color that have a same intra-cell position as the selected pixel wherein intra-cell position comprises pixels correspondingly located in half-tone cells for the predetermined non-black primary color; and if any of the obtained half-toned pixel data contains the predetermined non-black primary color and does not contain black, then modifying the half-toned pixel data for the selected pixel to include the predetermined non-black primary color using a computer processor.