This is interesting. I am red/green colorblind and my son played in some indoor leagues/tourneys this winter where, for some reason, they used a pink ball on green turf, in the already dark dome/pole building they were playing in. I had a very hard time following, and couldnt imagine trying to play under those circumstances.
I've seen discussion about a switch away from the standard white ball, particularly given all the winter and night games. I've also wondered if from a goalie perspective, it is more difficult to track a white ball, coming out of a white set up (head, mesh, shooters)?