We measured blur thresholds for square wave gratings modulated either along the red-green, the luminance or the yellow-blue colour direction. The modulations along the red-green and yellow-blue resulted in zero luminance variation. For all three observers the blur thresholds for red-green and luminance stimuli were very similar. The blur thresholds for yellow-blue were much higher. These results are consistent with the idea that the luminance and red-green channels do not differ in their inherent spatial resolution.
Huw C. Owens, Stephen Westland, Sophie Wuerger, "Blur tolerance and perceived sharpness in the chromatic and luminance domain" in Proc. IS&T 5th Color and Imaging Conf., 1997, pp 235 - 239, https://doi.org/10.2352/CIC.1997.5.1.art00046