The various colors, such as red, mauve, purple, violet, and blue in Hydrangea macrophylla are developed from myrtillin complexes with metal ions called metalloanthocyanins.[4]
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^Yoshida K, Mori M, Kondo T (2009). "Blue flower color development by anthocyanins: from chemical structure to cell physiology". Nat. Prod. Rep. 26 (7): 884–915. doi:10.1039/b800165k. PMID19554240.