Vayupurana 1.23.71

Vāyupurāṇa 1.23.71

yadā tu punarevāyaṃ kṛṣṇavarṇo bhayānakaḥ.
matkṛtena ca varṇena matkalpaḥ kṛṣṇa ucyate .. 23.68 ..