Natyashastra
मुखवर्णपरावृत्त्या नाडीपीडनयोगतः । वैवर्ण्यमभिनेतव्यं प्रयत्नात्तद्धि दुष्करम् ॥ १०५॥
Change of Colour should be represented by alteration of colour of the face by putting pressure on the artery, and this is dependent on the limbs.
english translation
mukhavarNaparAvRttyA nADIpIDanayogataH । vaivarNyamabhinetavyaM prayatnAttaddhi duSkaram ॥ 105॥
hk transliteration by Sanscript