Image sensor device includes color pixel array without color filter array. Method of color separation is based on tapering of light selectively depending on wavelength into photodetectors inside pixel. Light is directed into light guide along semiconductor surface with color selective structures and photodetectors in each pixel used to collect each light color component separately. This approach and horizontal geometry of light guide have numerous advantages, for example for the CMOS fabrication process, and allow multiple ways for detail engineering of light color components separation and detection.