PURPOSE: To form a picture which is not fogged by the mixing of the three primary colors by developing the picture successively with developing agents with cyani, magneta and yellow hues respectively.

CONSTITUTION: If the values of adsorption starting electrostatic latent potential and defined as cyanine (color C) 3<magenta (color M) 1 < yellow (color Y) 2 in respective developing agents, the higher potential shows the lower adsorption, namely, the developing agent with higher adsorption starting electrostatic latent potential is difficult to be adsorbed to the remaining charge on the surface of an already formed picture. When it is supposed that the quantity of the remaining charge after development is constant, fogging is more reduced by the development in the hue order of C3, M1, T2 at least in comparison with the order of Y2, M1, C3. Consequently, the development in the hue order of C3, M1, Y2 forms the most superior picture of 7 hues in comparison with other hue orders.