My lips are purple. I became a hemorrhoids surgery in June, 20 12, and often had abdominal distension and exhaust (fart) after operation. Later, I found that my lips were always purple.
The oxygen content in the air at high altitude is very low. In order to get more oxygen to meet the needs of the body, the body will automatically produce more hemoglobin to absorb oxygen in the air. Too much hemoglobin in the body can easily lead to purple lips and red face, which is people's adaptation and reaction to plateau life.