Lip discoloration is the change of a person’s natural lip color to a lightened or darkened shade. The most common discoloration tones are brown and gray; however, the lips can also turn to a blue or yellow tone, says Healthhype.com.
Lip discoloration can be attributed to environmental causes, chemical or mechanical damage, skin issues or systematic disease. Anemia is a common cause among women for lip discoloration, reports Healthhype.com. Smoking cigarettes may cause melanosis, which darkens the lips and the inside lining of the mouth. There are several other causes for dark lips, including cyanosis, dermatitis, dry lips, eating disorders, medications, Peutz-Jeghers syndrome and toxins.