The phrase "dark pigmentation" refers to the color of someone's skin, hair, or eyes. It means that these features are darker in shade compared to others. Full definition
The coat has a dense, harsh texture, and may be in any solid color: black, brown, gray, apricot, cream or white, with dark pigmentation of nose, lips and eye rims. (sheltieplanet.com)
We show that variants associated with dark pigmentation in Africans are identical by descent in South Asian and Australo - Melanesian populations. (science.sciencemag.org)
I get occasional hormonal breakouts, and suffer from dark pigmentation from the sun and natural freckling. (playdatesandpearls.com)