Blue jays appear blue due to light scattering in their feathers, not pigments. Their color can be changed to black by altering feather structure.
Blue iguanas of Grand Cayman have a long lifespan, turning bluer as they mature. They can change color and appear gray to blend with rocks. Males are more intensely blue than females.
Glaucus atlanticus, a colorful nudibranch, feeds on venomous Portuguese man o' war. Its blue color provides camouflage, and it can absorb the stingers for defense and hunting.
The mandarin dragonet is a vibrant fish with blue cellular pigment. It also features orange stripes and is popular in aquariums.
The blue poison dart frog's blue color warns predators of its poison. Its skin's cellular structure scatters blue light, creating the blue appearance.
Blue morpho butterflies' wings appear blue due to the nanostructure of their scales. Males are typically bluer than females, and the ventral side of their wings is brown.
Sinai agama lizards are typically brown but males turn bright blue during breeding season to attract females. Females may have red markings.
Linckia laevigata is a blue sea star found in the Indo-Pacific. Its coloration is caused by a pigment called linckiacyanin, giving it a unique blue hue.
Carpathian blue slugs in Eastern Europe change from yellow-brown to blue as they mature, with adults displaying various shades of blue.
The cottonmouth, or water moccasin, is a semi-aquatic pit viper found in the southeastern U.S. It has a powerful venom but is not overly aggressive. Care must be taken to distinguish it from harmless water snakes.