Provided herein are teachings directed to calibrating an output device such as a color display, using a visual method of determining the gamma for the blue primary that is easier to perform and more consistent than methodologies employing a luminance-matching task. The methodology is based on the insight that accurate gamma estimation for blue is important not for luminance reproduction, but for proper color-balance, and most importantly grey-balance. Thus, it follows to use grey-balancing, rather than luminance-matching, as the criterion for selecting the blue gamma value. One variant as taught herein is to provide a user visual task to find a patch best representing neutral, given previously determined calibrated digital values for the red and green primaries that produce 50% fractional luminance. A large patch is displayed within a larger surround containing both a white border and either a checkerboard or a line pattern, so as to establish a reference for the neutral axis. The user adjusts a control causing only the value of the blue primary to change. This changes the color of the patch in the middle, moving it along a line from yellowish to bluish. The user thus selects the value at which the patch appears most nearly neutral with respect to the surround. Effectively, the task is to match the chromaticity of a grey patch with that of a halftone pattern.