The Compendium of Caraka 2.2.24

2.2.24

yat kṛṣṇamathavā nīlaṃ yadvā śakradhanuṣprabham/
raktapittamasādhyaṃ tadvāsaso rañjanaṃ ca yat//

That which is black or blue, or resembles a rainbow,
and that raktapitta which stains cloth, is incurable;