Color sensing procedures typically involve multiple active., detectors or a photodetector coupled to a filter array We demonstrate the possibility of using a single polymer layer based device structure for multi-color sensing. The device structure does not require any color filters or any subpixelation, and it distinguishes colors without any external bias. The color sensing relies on an appropriate thickness of the active polymer layer that results in a characteristic polarity and temporal profile of the photocurrent signal in response to various incident colors. The device characteristics reveal interesting similarities to the features observed in natural photosensitive systems including retinal cone cells.