It might (obviously) tend to weed out the color blind, but I think these would be hard to crack: http://www.toledo-bend.com/colorblind/Ishihara.html http://www

It might (obviously) tend to weed out the color blind, but I think these would be hard to crack: http://www.toledo-bend.com/colorblind/Ishihara.html http://www.toledo-bend.com/colorblind/Ishihara.html