I'm not sure about all the other contrarians here that are somehow defending a cheap filter, but I don't think I need to remind everybody that we are playing AS the legends. Unless you all think that the players were controlled by spectators at home, then there's no reason to inexplicably think that the legends saw the world in black and white. What WOULD be cool is if the REPLAYS were in black and white, since it'd still be neat to have that little throwback to 'black and white sports'.
Contrary to popular belief, the first colour broadcast in 1954 did NOT magically colour the entire world.
But go ahead, please keep mixing up 'taking the high road' and 'willfully ignorant of poor game design', by telling us about how great a white ball being thrown against grey backdrops is, and how great dark grey pitching lines mesh well with slightly lighter grey meters.
The fact remains that it doesn't make sense from a gameplay or realism standpoint.