For healthy skin, collagen is key: This naturally occurring protein keeps skin smooth and youthful, but our bodies produce less collagen as we get older. The result? Thinner skin, dryness, and more wrinkles.
Definition of BLACK BILE. : a humor of medieval physiology believed to be secreted by the kidneys or spleen and to cause melancholy. ADVERTISEMENT.1681. a humor of medieval physiology believed to be secreted by the kidneys or spleen and to cause melancholy. ADVERTISEMENT. 1681.
from my own experience, what you refer to as black colon is also called  melanosis coli which means: it's a condition associated with chronic laxative use in which dark pigment is deposited in the lining layers of the large intestine(which is the colon). the pigment results in a characteristic dark brown to black lining of the large intestine.