Green or blue urine may be the result of a number of causes, many of which are harmless. These include artificial food dyes, certain medications and urinary tract infections, according to the Mayo Clinic.
The Mayo Clinic states that some brightly colored food dyes can turn urine green, and certain dyes used for kidney and bladder tests have a similar effect. Some of the medications that cause green urine include indomethacin, propofol and amitriptyline. Finally, medical conditions that may have this effect are urinary tract infections caused by pseudomonas bacteria and a rare genetic condition known as familial hypercalcemia.
The normal yellow color of urine is caused by a pigment known as urochrome, and depending on the concentration of water in the urine, the color can range from a pale, light yellow to a dark amber. According to WebMD, urine can take on a vast array of colors, and not every color change is cause for alarm. Medications and certain foods can turn urine bright orange, blue or fluorescent green. Urine that is pink or red likely contains blood, but it is important to remember that even a drop of blood can tint urine.
MedlinePlus advises individuals to contact their health care providers if their abnormal urine color persists. MedlinePlus also recommends that individuals contact a physician if they are unable to find an explainable cause for the abnormal color or if the urine contains blood.