Garudapurana 1.155.24

1.155.24

lakṣayellakṣaṇotkarṣādvātādīñchoṇitādiṣu /
aruṇaṃ nīlakṛṣṇaṃ vā sampraviśyanviśettamaḥ //

One should identify [the symptoms of] vāta and the rest in blood and other [substrates] by the prominence of symptoms. / Entering into red, blue, or black, he enters darkness;