The Compendium of Caraka 5.7.11

5.7.11

rūkṣā śyāvāruṇā yā tu vāyavī sā hataprabhā/
viśuddharaktā tvāgneyī dīptābhā darśanapriyā//

That which is rough, grayish, and reddish is the airy one, stripped of radiance;
that belonging to fire is pure red, brilliant in luster, and pleasant to behold;