Eggshells are primarily composed of calcium carbonate, a chemical compound that is white in its pure form. The color of an eggshell is determined by the presence of pigments in the outer layer of the shell. In the case of chicken eggs, the natural color of the eggshell is white.

The process of eggshell formation begins in the hen's oviduct, where layers of mineralized material, including calcium carbonate, are deposited onto the eggshell membrane. The presence of pigments, such as protoporphyrin and biliverdin, in the outer layer of the shell can give eggs a different color, such as brown or speckled. However, the base color of the eggshell remains white due to the inherent color of calcium carbonate.


Different bird species may have eggs with varying shell colors, ranging from white and brown to blue or green, depending on the specific pigments present. The color of eggshells is influenced by the genetics of the bird species.