What scriptures describe Vishnu's body being blackened by Vasuki?

Question

As I discuss in this answer, the Pancharatra Agamas are the foundational texts of Vaishnavism. Similarly, the foundational texts of Shaivism are known as the Shaiva Agamas, aka the Shaiva Tantras. One of the Shaiva Agamas is known as the Kirana Agama, and it takes the form of a dialogue between Shiva and Vishnu's bird Garuda.

In this excerpt from the Kirana Agama, Garuda says a hymn of praise to Shiva, and in particular he says this:

Victory to the Lord who quenched the virility of the deadly poison (emitted by the snake Vasuki at the time of the churning of the milky ocean) that blackened the body of Vishnu (who was then white in complexion); victory to the Lord who sustained the divine river Ganga that rushed forth from the heaven ... full of whirls and great conceit.

My question is, what scriptures describe Vishnu's body being blackened by Vasuki during the Churning of the Ocean?

This chapter of the Srimad Bhagavatam does describe Vasuki blackening the faces of the Devas, at least before Vishnu sends down rain to remedy the situation:

Vāsuki had thousands of eyes and mouths. From his mouths he breathed smoke and blazing fire, which affected the demons, headed by Pauloma, Kāleya, Bali and Ilvala. Thus the demons, who appeared like sarala trees burned by a forest fire, gradually became powerless. Because the demigods were also affected by the blazing breath of Vāsuki, their bodily lusters diminished, and their garments, garlands, weapons and faces were blackened by smoke. However, by the grace of the Supreme Personality of Godhead, clouds appeared on the sea, pouring torrents of rain, and breezes blew, carrying particles of water from the sea waves, to give the demigods relief.

And Vishnu's incarnation Ajita, the Manvantara Avatara of the Chakshusha Manvantara, was one of the Devas who participated in the churning of the Ocean. But are there any scriptures that specifically say that he was blackened? And is there any scriptural basis for the translator's claim that he was originally white?

On a side note, I suppose if Vishnu was originally white, that would lend support to the theory that the "shuklam bharadharam" shloka chanted before the Vishnu Sahasranamam is addressed to Vishnu rather than Ganesha or Vishvaksena.

Answer 1

According to Skanda Purana chapter 9, it was Kalakuta poison which made Lord Vishnu black or dark blue (color of Taamala).

91. The excellent mountain had adamantine strength. It rolled on the back, neck, thighs and the space between the knees of the noble-souled tortoise. Due to the friction of these two, submarine fire was generated.
92. The Halähala poison too emerged and it was seen by Närada.

Seeing the deadly poison Kaalkuta, all of them went to Satya Loka as suggested by Bhrigu Maharshi. But even Brahma on seeing the blazing Halalal couldn't help them and they all with Brahma flew to abode of Lord Vishnu.

107. Then Devas kept Brahmä at their head and hurriedly went to Vaikuntha, because they were afraid of Kälaküta.
108. Brahmä and others as well as the groups of sages sought refuge in the great lord Vishnu, the primordial Purusha, the mighty lord who had resorted to Vaikunta, Mädhava, Adhoksaja. The groups of Suras and Asuras sought refuge in lord Visou.
109. By that time, the great poison Kälaküta came there. After burning Brahma's world at the outset, it burned Vaikunta.
110. Visnu who dwells in the cavity of the heart of everyone, was burned by the fire of Kälaküta also with his attendants. Immediately he acquired the colour of Tamäla.
111. Vaikuntha also became blue in colour. It was surrounded by all the worlds. Hence, all the worlds became encircled by the poisonous substance from the waters.

Vayu Purana Chapter 54 also describes the same incident.

विषेणोतिष्ठमानेन कालानलसमविषा। निर्दग्धो रक्तगौराङ्गः कृतः कृष्णो जनार्दनः॥ ५९॥

Janardana Visnu who was fair and reddish in complexion has been burnt by the poison that rises with lustre of black fire. He was rendered dark-complexioned.

दृष्ट्रा तं रक्तगौराङ्गं कृतं कृष्णं जनार्दनम्। भीताः सर्वे वयं देवास्त्वामेव शरणं गताः॥ ६० ॥

Having seen that whitish red-hued Janardana, rendered dark-complexioned one, all of us got frightened. We seek refuge under you.

सुराणामसुराणां च श्रुत्वा वाक्यं पितामहः। प्रत्युवाच महातेजा लोकानां हितकाम्यया॥६१॥

Having listened to the Words of the gods and demons, highly radiant Pitamaha Brahma replied, out of desire for the beneficence of the worlds.

शृणुध्वं देवताः सर्वे ऋषयश्च तपोधनाः। तत्तदग्रे समुत्पन्नं मथ्यमाने महोदधौ॥ ६२॥
विर्ष कालानलप्रख्यं कालकूटेति विश्रुतम्। येन प्रोद्भूतमात्रेण कृतः कृष्णो जनार्दनः॥६३॥

"O you Devas, sages and saints, all of you listen. The poison, resembling black fire, that rose up when the great ocean was being churned is known as Kalakuta. Even as it rose up, (Visnu) was rendered black.

The Verse from Kirana Aagana mentions the poison as Kalakuta which emerged during churning of ocean. Commentator misinterpreted Kalakuta as poison of Vasuki.