A three-color sensor array based on a vertically integrated thin-film structure is reported. The complete color information can be detected at the same position of a sensor array without using optical filters. The sensors consist of a multilayer thin-film system utilizing amorphous silicon and its alloys. The spectral sensitivity of the sensors is controlled by the optical properties of the materials and the applied bias voltage. The color sensors were integrated with amorphous silicon readout electronics to realize a large area thin-film three color sensor array. The working principle of the thin-film sensor arrays is presented with a discussion of the spectral sensitivity and the pixel cross talk.