there are other two genes(that we know of) that can enhance the appearance of eggs, the shiny egg trait and the Translucent egg trait. when combined with Blue and white egg shell the effect is just beautifulNot much to it. Genetically there is only three colors of eggs. White, brown or blue. Selection can enhance the expression of the traits like the darker brown eggs in Marans. Still just a brown egg gene but those birds deposit more brown pigment than others. The blue is dominant over the white but mixes with the brown to produce the the greenish eggs often seen in ameraucanas. There is no gene for green it's just a mix of brown and blue. Certainly no gene for chickens to lay pink eggs. Just three color genes, white, brown or blue.