For over 30 years there has been a controversy over whether
color-defined motion can be perceived by the human visual system. Some
results suggest that there is no chromatic motion mechanism at all,
whereas others do find evidence for a purely chromatic motion
mechanism. Here we examine the chromatic input to global motion
processing for a range of color directions in the photopic luminance
range. We measure contrast thresholds for global motion identification
and simple detection using sparse random-dot kinematograms. The results
show a discrepancy between the two chromatic axes: whereas it is
possible for observers to perform the global motion task for stimuli
modulated along the red–green axis, we could not assess the
contrast threshold required for stimuli modulated along the
yellowish-violet axis. The contrast required for detection for both
axes, however, are well below the contrasts required for global motion
identification. We conclude that there is a significant red–green
input to global motion processing providing further evidence for the
involvement of the parvocellular pathway. The lack of S-cone input to
global motion processing suggests that the koniocellular pathway
mediates the detection but not the processing of complex motion for our
parameter range.