We propose estimating the gamma value for the blue channel of a softcopy display via a grey-balancing task. A “near-neutral” patch is displayed along with a neutral reference pattern made from black and white pixels. The red and green values for this near-neutral patch are derived from a separate calibration of these 2 channels. The user then adjusts the blue value until the near-neutral patch appears neutral with respect to the surrounding reference. Gamma for the blue channel is estimated from the selected value. Implementations include interactive adjustment with mouse and/or keyboard, or selecting from a fixed set of patches the one that appears most neutral. When compared with the standard technique, inter- and intra-observer variation in the settings for blue were substantially reduced.