Garudapurana 2.6.21

2.6.21

pītavarṇo bhavedvaiśyaḥ śūdraḥ kṛṣṇaḥ smṛto budhaiḥ /
yathāvarṇaṃ samuddiṣṭo varṇeṣu brāhmaṇādiṣu //

a yellow-colored one belongs to a vaiśya, and a black one is remembered by the wise for a śūdra; / [each] is prescribed according to caste, among the castes beginning with brahmins.