A set of screens is provided for use in printing respective color separations in a halftone color printing process. This set of screens comprises at least two clustered-dot screens and the frequency and angle parameter values of the screens is such that the lowest frequency moiré produced by any combination of at least two frequency components, taken from the group comprising the first and second screen harmonics, for which the sum of the harmonic orders of the frequency components in the combination is less than a predetermined value, is of a sufficiently high frequency as to be substantially unperceivable to the human visual system; other moirés are also substantially unperceivable to the human visual system. The lowest frequency moiré serves to reduce the visibility of color changes caused by color plane registration variations. A printing system and method employing the screen set are also provided.