Abstract: The average color, and excursions outside predetermined acceptable color limits, of non-solid-shade fabrics, such as denim, can be determined utilizing a filter colorimeter, an A/D convertor, and computer. A swatch of fabric having a length greater than its width is continuously moved past the colorimeter, and is continuously sampled at the rate of at least about 100 readings per second until the length of the entire swatch has been sampled and analog signals have been generated for all readings. Analog signals are continuously passed from the colorimeter to the A/D convertor, and from the convertor as digital signals to storage in the computer. After sampling is completed the stored digital signals are analyzed. The voltage of the electric light source of the colorimeter is monitored to calibrate the digital signals depending on the voltage to the light source.