On probiotic for about a week. bm was yellowish, now its dark green mixed with yellow. looks like alot of undigested material. are they working?

Not necessarily: A yellowish stool can mean there is excess fat in the stool. When you take probiotics you are altering the bacteria in the intestine, so stool changing color would be common, though not necessarily green. Green is sometimes associated with food moving through the large intestine too quickly, with incomplete processing by bile. Add fiber, whole grain cereal/bread, to slow stool transit time.