Complementary colors of guṇa avatāra
Tamas guṇa (nīla śaktī – kṛīṁ bīja) is of dark black color, therefore complementary Rudra is always of white color
Sattva guṇa (śrī śaktī – śrīṁ bīja) is of white color, therefore complementary Viṣṇu is always of dark black color
Rajas guṇa (bhū śaktī – hrīṁ bīja) is of blue color, therefore complementary Brahmā is always of yellow color
Whenever God is to be represented in three forms, the colors need to be black, white and yellow that will sustain sattva, subdue tamas and control the overactive rajas respectively.