THE familiar color of urine may dramatically depart from yellow to assume various shades of white, orange, green, red, brown, and black. This urinary rainbow contains a treasure of clinical clues to the physician, who reads them correctly. For example, milky white urine may be the result of pus, phosphate crystals, or occasionally chyle. The first two can be separated by centrifugation and then identified microscopically. It may not even be necessary to do this if the urine pH is below 7.0, for phosphates will not precipitate in acid urine. Chyle is also associated with an alkaline urine, and is identified by its extractability with fat solvents. Green urine represents a mixture of blue and yellow. Therefore, a Pseudomonas infection (blue pus) or ingestion of a methylene blue dye will combine with the normal yellow urochrome and emerge as green. The spectrum of red, brown , and black should be separated