My Lord, Your form is transcendental to the three material modes, yet for the maintenance of the three worlds, You assume the white color of Viṣṇu in goodness; for creation, which is surrounded by the quality of passion, You appear reddish; and at the end, when there is a need for annihilation, which is surrounded by ignorance, You appear blackish.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
स त्वं त्रिलोकस्थितये स्वमायया बिभर्षि शुक्लं खलु वर्णमात्मनः । सर्गाय रक्तं रजसोपबृंहितं कृष्णं च वर्णं तमसा जनात्यये
sa tvaṃ trilokasthitaye svamāyayā bibharṣi śuklaṃ khalu varṇamātmanaḥ | sargāya raktaṃ rajasopabṛṃhitaṃ kṛṣṇaṃ ca varṇaṃ tamasā janātyaye
SB 10.3.20