Bhagavatapurana 12.8.32

32. When he (the sage) was thus absolutely devoting his mind (to Him) by means of Tapas, study of the Vedas and self-control, Sri Hari in the forms of Nara and Narayana revealed Himself unto him to bestow His grace on him.

33. & 34 They (Nara and Narayana) were (respectively) of white and blue complexions, beautiful with eyes like unto fresh-blown lotuses, and with their four arms; they were clad in dear-skin (bark), held sacred grass in their hands; wore the sacred thread of triple fibres; carried with them a pitcher (Kamandalu) and a bamboo staff; a fan (to drive away insects like mosquitoes) and a string of beads (lotus-seeds); they were of high stature and by their golden hue like the flashing streaks of lightning, were in two forms nothing but Tapas itself, and worshipped by the great gods.