"Normal rabbit urine varies in colour from yellow to orange, brown or red depending on nutrition and hydration status and may be influenced by medication." 
"The normal color of urine from rabbits is yellow. Sometimes the urine can become red, pink, brown, or orange. This condition, often simply called 'red urine,' can occur in healthy rabbits as well as those who are ill." Causes can be: plant pigments, antibiotics, stress, dehydration, blood, and bilirubin or urobilinogen.
- Kinenchen, Guide to Bunny Pee - Pictures (Graphic)
- Greendale Veterinary Diagnostics, Rabbit Urinalysis
- PetEducation.com, Causes of 'red urine'
- The Rabbit Haven, Dr. Carolynn Harvey, DVM, Rabbit Urinary Tract Issues
- PetPlace.com, Urinary Disorders in Rabbits
- Ontario Rabbit Eduction Organization, Urinary
- RabbitsOnline.net, Urinary Tract Problems
- eXtension, Urinary Tract Diseases in Rabbits: Introduction
The following are a few helpful videos on the topic: