Why is Krishna portrayed to be blue?
Krishna's color is quoted from scripture to be like the hue of newly formed rain clouds. See Brahma Samhita 5.30:
veṇuṁ kvaṇantam aravinda-dalāyatākṣam-
govindam ādi-puruṣaṁ tam ahaṁ bhajāmi
For the full word for word translation, see Bhaktivedanta VedaBase. An overall translation is below:
I worship Govinda, the primeval Lord, who is adept in playing on His flute, with blooming eyes like lotus petals with head decked with peacock's feather, with the figure of beauty tinged with the hue of blue clouds, and His unique loveliness charming millions of Cupids.
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