Tattoos bleed, and a clear fluid known as "serious drainage" is usual during the procedure and for a day or two afterwards. It is typical for the tattoo to drain clear fluid, as well as ink. It is typical for a tattoo to drain the color or colors contained inside it. If another color is used, it will usually be an opaque black. Ink that remains in the skin is absorbed by macrophages, which are cells that eat foreign material. The ink is broken down over time and removed from the body through urine and feces. There have been reports of people who continue to see flashes of colored light after their tattoos have healed for several years, which shows that some of the ink may still be visible even after it has been absorbed by the body.