(A) To account for the possibility of luminance differences between stimuli due to different color sensitivities in macaques and humans, we performed a psychophysical experiment using a no-report minimum motion technique based on eye-movements in a third macaque monkey. We presented moving gratings consisting of alternating frames with luminance and color contrasts, respectively, with each frame being shifted by a quarter cycle for 500 ms. Color contrasts consisted of a reference gray and a color to be probed. If the probed color was darker than the reference gray, motion in one direction was perceived, if it was brighter, in the opposite direction. A color equiluminant to the reference gray should not evoke any stable motion percept. Stimuli were presented in two conditions: either a brighter probe color elicited upwards motion, or downwards motion. (B) This technique was applied to colors of 8 different hues, at 19 luminance levels. (C) We computed a luminance difference index based on eye position measurements, by calculating the difference in vertical eye trace curvature between conditions. For a color equiluminant to the reference gray, this measure was expected to be 0. The left plots show the luminance difference measure resolved in time, the right plots show the average over time. For all colors, 0 was crossed within the range of luminances probed, suggesting that this range included colors equiluminant to the reference gray. There was a significantly positive slope (pearson correlation, p<0.05) for 6 out of 8 colors, validating our approach. (D) Estimates of the zero-crossing for all eight hues are close to the L value of the reference gray, suggesting that psychophysically equiluminant colors in the macaque are close to those derived from human L*C*h - space. Shaded area shows 95% bootstrap confidence interval.