A very common carotenoid in animals is astaxanthin, which gives off a purple-blue and green pigment. Astaxanthin’s color is formed by creating complexes with proteins in a certain order. For example, the crustochrin has approximately 20 astaxanthin molecules bonded with protein. When the complexes interact by exciton-exciton interaction, it lowers the absorbance maximum, changing the different color pigments.
In lobsters, there are various types of astaxanthin-protein complexes present. The first one is crustacyanin (max 632 nm), a slate-blue pigment found in the lobster’s carapace. The second one is crustochrin (max 409), a yellow pigment which is found on the outer layer of the carapace. Lastly, the lipoglycoprotein and ovoverdin forms a bright green pigment that is usually present in the outer layers of the carapace and the lobster eggs