While Brahma was contemplating, all the calves and cowherd boys immediately transformed into visnu-murtis, having bluish complexions and wearing yellow garments

Expressions researched:
"While Brahmā was contemplating, all the calves and cowherd boys immediately transformed into viṣṇu-mūrtis, having bluish complexions and wearing yellow garments"

Srimad-Bhagavatam

SB Canto 10.1 to 10.13

While Brahmā was contemplating, all the calves and cowherd boys immediately transformed into viṣṇu-mūrtis, having bluish complexions and wearing yellow garments. Brahmā was contemplating his own power and the immense, unlimited power of Kṛṣṇa, but before he could come to a conclusion, he saw this immediate transformation.

SB 10.13.46, Translation and Purport

Then, while Lord Brahmā looked on, all the calves and the boys tending them immediately appeared to have complexions the color of bluish rainclouds and to be dressed in yellow silken garments.

While Brahmā was contemplating, all the calves and cowherd boys immediately transformed into viṣṇu-mūrtis, having bluish complexions and wearing yellow garments. Brahmā was contemplating his own power and the immense, unlimited power of Kṛṣṇa, but before he could come to a conclusion, he saw this immediate transformation.