“The shyama color is not exactly blackish. Shrila Bhaktisiddhanta Sarasvati Thakura compares it to the color of the atasi flower. It is not that Lord Krishna Himself appears in a blackish color in all the Dvapara-yugas. In other Dvapara-yugas, previous to Lord Krishna's appearance, the Supreme Lord appeared in a greenish body by His own personal expansion. This is mentioned in the Vishnu Purana, Hari-vamsha and Mahabharata.” (Shrila Prabhupada, Chaitanya Charitamrita, Madhya 20.337, Purport)