From Colors of Religion: Buddhism.
The principle colors involved in Buddhism are Blue, Black, White, Red, Green, and Yellow, and each — except for Black — are aligned to a specific Buddha.
See Five Wisdom Buddhas for the five qualities of the Buddha and each Buddha’s color.
Each of the five Buddhas first identifies a specific human failing and then helps us in transforming it into a positive attribute, bringing about the spiritual evolution required for enlightenment.
The Five Buddha Families and the Eight Consciousnesses by Thrangu Rinpoche, Geshe Lharampa. Translated by Peter Roberts. (Pdf)