Genesis 30:37-40

Jacob, however, took fresh-cut branches from poplar, almond and plane trees and made white stripes on them by peeling the bark and exposing the white inner wood of the branches. Then he placed the peeled branches in all the watering troughs, so that they would be directly in front of the flocks when they came to drink. When the flocks were in heat and came to drink, they mated in front of the branches. And they bore young that were streaked or speckled or spotted. Jacob set apart the young of the flock by themselves, but made the rest face the streaked and dark-colored animals that belonged to Laban. Thus he made separate flocks for himself and did not put them with Laban’s animals.