'Streaks' in the Bible

Meanwhile, Jacob kept tending the rest of Laban's flock. Jacob took branches from white poplar trees, freshly cut almond trees, and some other trees, stripped off their bark to make white streaks, and uncovered the white part inside the branches.

He is to determine if the contagion is indeed on the walls of the house, with greenish or reddish streaks, and to determine if it appears to be deeper than the surface of the wall.