I found this on a site about cotton tails and this is what it says about their urine: The normal urine pH is 8.2. The urine of young rabbits is free of precipitate but albuminuria is normal; the urine of mature rabbits is cloudy due to the presence of ammonium magnesium phosphate and calcium carbonate crystals. The color may vary from tan to reddish-orange, the latter color being due to the presence of porphyrin and bilirubin derivatives.
Now I wonder why it is blue. Is there anything you can do to help them?