Efficient mineral beneficiation requires process-control sensors that measure product grades quickly and accurately. The U.S. Bureau of Mines has developed a sensor system that uses color to instantaneously measure mineral concentrations in flotation froths and other process streams. Information from color measurements could significantly augment X-ray fluorescence and neutron-activation analyses currently used to control beneficiation processes. The color sensor system consists of a color video camera, a video-capture board, a computer, and a Bureau-developed computer program that evaluates the color information. A major innovation is the use of the color vector (a calibration standard from commercial broadcasting) to estimate composition. Color vector angles are an excellent measure of the subtle color changes resulting from differences in mineral concentrations. The compositions of dry mineral mixtures, slurries of mixed minerals, and mineralized flotation froths were evaluated with the color sensor system. Color measurements correlated well with mineral composition in each of these cases, thus demonstrating the potential to provide instantaneous on-line information about froth composition for process control.