Multi-pass type color image forming apparatus and method

A color image forming apparatus includes a photoreceptor medium, an exposing unit, a plurality of developer units, and a power supply. The exposing unit scans light onto the photoreceptor drum to form a latent electrostatic image. The plurality of developer units include developer rollers supplying toner to the latent electrostatic image to develop the latent electrostatic image into a toner image. Each developer unit contains toner of a different color, and the developer units are arranged around the photoreceptor medium so that the developer rollers are separated by a development gap from the photoreceptor medium. The power supply selectively applies a first bias allowing toner to be supplied through the development gap to the photoreceptor medium on which the latent electrostatic image is formed and a second bias preventing toner from passing through the development gap.