The magnitude of Melanin pigmentation of the lips depends on ones complexion (skin colour) But if you want to make it look pink it can be done using laser . The procedure is painless but post operatively there can be soreness for a few days and will subside with painkillers . The treatment outcome lasts for a few years . YAG lasers are used by dermatologists and most of the dentist have diode lasers and can be done in a dental clinic or with a dermatologist. A through medical history is required prior to the procedure to rule out other causes of hyperpigmentation .

It is pigmentation. And it varies from person to person depending on skin colour and hereditary too.