A new design of a color sensor circuit that can differentiate four colors and produce digital outputs is presented in this paper. The proposed circuit uses a photodiode as a light transducer and few additional electronic components. The advantage of the proposed architecture is that the number of required components is fixed regardless of the number of detected colors with only increasing the number of component inputs. This feature is important especially in element count and low power consumption. The sensor circuit is implemented on a breadboard with commercially available off-the-shelf electronic components. The objective of this work is to validate a new architecture of color sensor circuit design using simulation and experimental analysis as a proof of concept for a future implementation as integrated circuit. © IEICE 2011.