Mindstorms EV3 Tutorial #6: Use the color sensor to follow a line - YouTube
Lego Mindstorms NXT Color RGB Sensor 9694 – MSU Surplus Store
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Amazon.com: LEGO MINDSTORMS EV3 Building Set Includes 3 Interactive Servo Motors, Remote Control, Improved And Redesigned Color Sensor, Redesigned Touch Sensor, Infrared Sensor And 550+ LEGO Technic Elements : Toys & Games