We report preliminary results of an experiment measuring contrast sensitivity as a function of spatial frequency, location in color space and direction of variation. Observers viewed bipartite fields containing sinusoidal gratings on one side and a uniform field on the other, having the same mean color. The experiment used a forced choice paradigm to measure thresholds for a large number of observers and a large number of mean color/spatial frequency/direction of variation combinations, although no one observer saw every combination. While early data is noisy, we have found contrast sensitivity as a function of spatial frequency, on average, when any of L*, a*, b*, C* or H_ab is varied. We have not yet found any meaningful dependency on any independent variable other than spatial frequency, such as C*, as would be expected from such color difference metrics as CIE ΔE₉₄ or ΔE_CMC.