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.