Human eye color and reaction time.
Response latencies to a visual stimulus were determined for 44 male and 82 female Caucasians. Those with dark eyes had significantly shorter simple (one stimulus) reaction times. Complex (one of four stimuli) reaction times showed a similar, but nonsignificant, trend. Data from an additional 206 male Caucasians  on a one-trial non-practiced reaction task followed the same nonsignificant trend. Darker iris pigmentation apparently correlates with shorter reaction times but more strongly on practiced tasks and on those which do not involve accuracy.
D005127:Eye Color; D005260:Female; D006801:Humans; D008297:Male; D009048:Motor Skills; D011214:Practice, Psychological; D011930:Reaction Time; D014796:Visual Perception