In conventional halftone screen technology, orthogonal screens are widely used. The screen angles for three colors of cyan (C), black (K) and magenta (M) are 15°, 45° and 75°. Another one yellow (Y) is 0° or 30°. Since Y crosses to M (C) with the shallow angle difference of 15° when Y is 0°, a low frequency moiré occurs in red (green), and it becomes an image defect. In the xerography process that uses the multiplex transfer of color toners, more remarkable moiré especially occurs as compared with offset printing. In order to reduce this moiré, “four-color harmonics screen” which sets spatial frequency components in four colors as a harmonics relation, has been developed. This is achieved by sharing a part of spatial frequency between two colors using a nonorthogonal screen. There are two kinds of combination of four colors that have such a relation. One is a ring coupling that shares one spatial frequency component between two colors respectively, and combines four colors to the shape of a ring. Another is a star coupling. In this case, three colors share three spatial frequency components of remainder one color respectively. In this paper, two screen-sets are introduced as each example of screen designing. In conventional halftoning, a color moire could not sufficiently be prevented, if a high-frequency screen like 300 lpi was not used. However, a color moiré can be prevented by “four-color harmonics screen” even if the screen-frequency is 150 to 200 lpi.