A two-coloured lobster caught by Digby County (Nova Scotia) fisherman Edward Pothier. Tina Comeau photo
Lobster color derives from the presence of three different pigments: red, yellow, and blue. These colors typically mix to form a greenish-brown color. It is not uncommon to get a developmental error that inhibits the accumulation of red and yellow pigment, thus producing a blue lobster. Rarer is a two colored lobster. Because the two sides of lobster develop independently of each other an error can occur on one side an not the other. Most likely this occurs at a very early cell division stage and thus all alter cells on that half are also affected.