Undesired moire patterns may appear in color separation due to several different reasons. One of the most important ones is the interference between the halftone screens of the different primary colors, due to an improper selection or alignment of their frequencies and orientations. The author demystifies this moire phenomenon, by giving a clear, rather informal but illustrative explanation of the problem, and by pointing out some possible ways to avoid, or at least to minimize, its adverse effects on color separation