It's a common knowledge that different breeds of chickens lay different colored eggs. Here I'll explain what chemicals and conditions give rise to these differences.
White eggsAll eggshells are made of calcium carbonate and the white ones have no pigment added.Brown eggsThe brown colour is caused by protoporphyrin IX, from the hen's haemoglobin, and is coated on the outside of the egg as it moves through the oviduct.Blue eggsBlue eggshells have the pigment oocyanin, which does permeate the shell, so the blue coloring will be all the way through.Green eggsIf a brown layer and a blue layer are crossbred, chances are you will get a green egg when the protoporphyrin IX layer is deposited over the blue oocyanin shell.Pink eggsThe pinkish tint to an egg comes from the bloom or cuticle, a natural coating that seals the eggshell's pores. The bloom is often washed off before eggs are sold commercially.Speckled eggsSpeckled eggs can be laid by any hen with pigmented shells and comes from the egg rotating slower than normal during the pigmenting stage.Unlike the outside of an egg, the color and taste of its contents is affected by the chicken's diet and living conditions.
