The short answer is "none." Generally speaking, hens with white feathers (such as White Leghorns) lay white eggs and hens with reddish brown feathers (such as Rhode Island Reds) lay brown eggs. Shell color has little relationship to egg quality, flavor, nutritive value, cooking characteristics, or shell strength.
The color of brown eggs is a natural pigment placed by the hen on the surface of the shell during the final stages of egg formation. From the inside, the shell appears white. The outer shell color can vary from light to dark brown, depending on the breed of the hen and also on individual hen characteristics.