Charles Ellicott Commentary Genesis 30:40

"And Jacob separated the lambs, and set the faces of the flocks toward the ringstreaked and all the black in the flock of Laban: and he put his own droves apart, and put them not unto Laban`s flock." — Genesis 30:40 (ASV)

Jacob ... set the faces of the flocks toward ... — As the speckled lambs and kids would for some time remain with Laban’s flocks, this may perhaps mean that, when driving them to water, Jacob placed all the striped kids and dark lambs together, so that, by being in a mass, they might influence the imagination of the ewes and she-goats. Finally, after these had conceived, he drove the parti-colored young away to his own flocks.