What determines the color of the eggs of a domestic chicken?

Egg color is determined by the genetics of the hens. The breed of the hen will indicate what color eggs she will produce. For example, Leghorn chickens lay white eggs while Orpington’s lay brown eggs and Ameraucana produce blue eggs. An interesting tip is to look at the chicken’s ear lobes; typically those with white ear lobes produce white eggs.

All eggs start out white in color; those that are laid in shades other than white have pigments deposited on them as the eggs travel through the hen’s oviduct. The journey through the chicken’s oviduct takes approximately 26 hours. The shell takes roughly 20 hours to be complete. Ameraucana birds have the pigment oocyanin deposited on the egg as it travels through the oviduct. This pigment permeates the egg shell resulting in the interior and exterior of the egg being the same blue color. Chickens that lay brown tinted eggs deposit the pigment protoporphyrin on the eggs late in the process of forming the shell. The pigment therefore does not penetrate the interior of the egg, but tints only the surface of the egg, which is why brown eggs are white on the interior. In the case of an Olive Egger, a brown pigment overlays a blue egg shell resulting in a green egg. The darker the brown pigment the more olive color of the resulting egg.

Other than appearance, there are no major differences between eggs from different breeds of chickens.