Garudapurana 1.68.22

1.68.22

The brāhmaṇa's [diamond] should be white like a conch, a white water-lily, or rock crystal; the kṣatriya's should shine like the eyes of a hare or a mongoose;
the vaiśya's resembles a lovely plantain leaf; the śūdra's has the lustre of a polished sword.