Lesion discrimination under white light examination based on lesion color has been previously described in the literature. Red (also known as clear and/or pink) lesions are considered to be active and early lesions on endometriosis. White lesions may indicate areas of fibrosis and may be latent or dormant lesion of endometriosis. The red and white lesions are also known as the "subtle" lesions of endometriosis. Black (also known as brown, chocolate green, purple or blue) represent a more severe stage of the disease. Black lesions are also known as "gunshot" or "powder-burn" lesions and are considered the "typical" lesions of endometriosis. Mixed color lesions can include a mixture of any color. It has been speculated that the subtle lesions of endometriosis are more likely to be positive lesions and to be missed under white light examination. The red lesions are also considered to have more vessels of smaller diameter and may also include peritoneal microlesions and therefore may be more easily detected under NBI.