A color calibration system includes a visual display terminal (VDT), a color calibration sensor optically coupled to the VDT, and a computer processing unit (CPU) electrically coupled to the VDT and the color calibration sensor. The VDT has a display screen and a plurality of color channels, each color channel having an intensity input, a bias input, and a gain input. The VDT produces an image on the display screen responsive to the intensity input. The color calibration sensor provides values responsive to the chromaticity and luminance of a test patch portion of the image on the display screen. The CPU performs calibration of the VDT including setting the bias of each color channel to reduce the difference between a target black point and the test patch with the intensity input at a minimum value for each color channel.