Which preposition to use with pigmentation

around Occurrences 1%

The breasts may reach almost the size of the female's and there may be a well-marked area of pigmentation around the nipple.

in Occurrences 1%

Davenport has concluded that there are two double factors for black pigmentation in the full-blooded negro which are separately inheritable.

of Occurrences 1%

He was particularly struck by the change in the pigmentation of the skin, so much so that his own designation for the affection was "bronzed skin."

Which preposition to use with  pigmentation