1. A method for forming a color image comprising steps of (a) uniformly applying a primary charge to a photoreceptor comprised thereon of a conductive substrate, a photoconductive layer and an electrically insulating layer, wherein one of said layers is provided with plural kinds of color separating means being finely divided into units, (b) exposing said photoreceptor to light given from a color original and simultaneously applying a secondary charge, said secondary charge being one of an alternating current and a direct current with a polarity opposite to that of said primary charge, (c) uniformly exposing said photoreceptor to a color light capable of passing through at least one kind of said color separating means to form an electrically charged image pattern, (d) developing said electrically charged pattern with a developer comprising a color toner by developing means to form a toner pattern and applying a charge which is one of an alternating current and a direct current with a polarity opposite to that of said primary charge, (e) repeating steps (c) and (d) at least once more, provided that the color light and the color toner each different from these in the every previous steps are used, (f) transferring said toner pattern onto an image pattern receiving materials, and (g) fixing said image patterns transferred on said image pattern receiving material, wherein an area of said toner image pattern formed on an individual unit of said color separating means is larger than an area of said individual unit in a ratio within the range of 1.1 to 10.0.