The natural color of the urine varies from a light straw color to a yellow brown. The color is derived from the coloring matter of the blood. When urine is very abundant, its color is light; and when scanty, it is high colored.

In disease and various morbid conditions, the urine may become entirely colorless, or it may be deep red, green, blue, or olive color. In some cases, it even has a blackish hue. The deep red color is often present in fever. Olive color occurs in jaundice, and is due to the presence of bile in the urine.

When bile is present, the foam produced by shaking the urine in a bottle also has a deep yellow color. The presence of bile may be detected by placing a few drops of urine upon a piece of white porcelain or in a saucer, and adding a few drops of nitric acid. Rings of color will be seen spreading out from the point where the drop of acid was added. Various changes occur. The play of colors begins with green, and passes through olive, violet, blue, and red or yellow. The green color is characteristic of bile.

A dark brown or black color present in urine when passed, is due to blood in the urine. A black color appearing after the urine has set for some time is not particularly significant. Blue and green colors are very rarely seen. They are sometimes observed in cases of chronic inflammation of the kidneys. Peculiar coloration of urine is often induced by the use of medicines of various kinds. Black color is produced by carbolic acid and creosote. The urine is colored yellow by rhubarb and santonine. Senna gives to it a brown color, and turpentine, violet.