Increased Amount of Black Pigment

This page is the CodyCross answer for the clue below from Botanical Garden, Group 1428, Puzzle 1 (Hydrangeas).

Question is: Increased Amount of Black Pigment

and the answer is: MELANISM

Word Meaning:

MELANISM — Congenital abundance or excess of melanin pigmentation in the skin, hair, feathers and/or eyes, more than is typical for the species.

Definitions from Wiktionary.