This is because of a dark pigment that protects the skin.

His reasoning is that dark pigments take up more room in the fibers which cannot then "used" by the liquid.

The legs are yellow with some dark brown pigment.

Sometimes you might see dark brown pigments near the shoulders and between the armpits.

For example, some class rings are coated with a dark pigment to reduce their shininess.

Traces of dark pigment suggest that it was once painted.

Two things occurred to him as he watched the dark green pigment soak into his work boot.

It extends black and dark brown pigment throughout the plumage.

The amount of dark pigment on the belly varies from virtually nothing to almost completely black.

A dark golden pigment had been oiled into her, and it contained the scent.