My mother says the litter she has changes color when certain hormones and chemicals are off balance in the cats body. BUT that it really sucks for a gage in health because if you dont watch it immediatly after the cat uses it , the ammonia always changes the color. Her vote.... not worth it.
My moms cat is 17 and always has something small wrong with him. And if that litter hasnt helped her much.. i think i would agree?
good luck!