Shiva Purana

siva.sh/siva-purana/uma-samhita/27/19

ततस्तु तमसि ध्यायन्पश्यते ज्योतिरैश्वरम्।। श्वेतं रक्तं तथा पीतं कृष्णमिन्द्रधनुष्प्रभम् ।। १९।।

sanskrit

Thereafter while meditating in darkness he sees the bright lustre of Śiva in colours white, red, yellow, black and the rainbow colour.

english translation

tatastu tamasi dhyAyanpazyate jyotiraizvaram|| zvetaM raktaM tathA pItaM kRSNamindradhanuSprabham || 19||

hk transliteration by Sanscript