Colors.

Scientific American 2, 8.7.1868

It has been found, while firing at the "running man" target, at Wimbledon, England, which is scarlet on one side and gray on the other, that the scarlet dazzles the eye, and is hence the most difficult to hit, from leaving a red streak behind it, which unsettles the aim. The gray side was struck seventy-four times and the red only forty-two times. It is a curious fact, too, that those with gray eyes hit fairer than those with eyes of other colors.