No matter what the breed or what color the egg ultimately ends up being, all eggshells are white when they start their journey down the oviduct. This journey takes about 26 hours, the shell taking roughly 20 hours to be completed. In the last 4-6 hours of the laying process brown eggs 'turn' brown. A hen spending too much time in the sunlight can actually have a bleaching effect on the color egg that a hen lays, as can not having access to cool water.