Have you fed anything like beetroot to them at all? or chard? That may account for a reddish tinge to the urine..if not I would be looking at a vet appointment asap, unless other more experienced piggy owners have an alternative.. The source of this experience was we fed a bistro salad mix for variety over a couple of days, and the pee had a red tinge..we were scheduled to take our ill little piggy to the vets, always with the Roz for companionship at that stage, and vet said beetroot and chard! Hopefully don't worry much. If it is actual blood get then seen asap of course!