Chandogya Upanishad 6.4.2

6.4.2

yad ādityasya rohitaṃ rūpaṃ tejasas tad rūpam \
yac chuklaṃ tad apām \
yat kṛṣṇaṃ tad annasya \
apāgād ādityād ādityatvam \
vācārambhaṇaṃ vikāro nāmadheyaṃ trīṇi rūpāṇīty eva satyam \\604.2\

2. Whatever red form the sun has, is the form of heat; whatever white, the form of water; whatever dark, the form of food. The sunhood has gone from the sun: the modification is merely a verbal distinction, a name. The reality is just "the three forms."