 The blue iguana is the largest native land animal on Grand Cayman with a total nose @-@ to @-@ tail length of 5 ft ( 1 @.@ 5 m ) and weighing as much as 30 lb ( 14 kg ) . It may be the heaviest species of iguana and most massive lizard in the Western Hemisphere . Its body length is 20 – 30 inches ( 51 – 76 cm ) with a tail equal in length . The blue iguana 's toes are articulated to be efficient in digging and climbing trees . Although not known to be arboreal , the blue iguana has been observed climbing trees 15 feet ( 4 @.@ 6 m ) and higher . The male is larger than the female by one third of his body size . The mature male 's skin color ranges from dark grey to turquoise blue , whereas the female is more olive green to pale blue . Young animals tend to be uniformly dark brown or green with faint darker banding . When they first emerge from the nest the neonates have an intricate pattern of eight dark dorsal chevrons from the crest of their necks to their pelvic area . These markings fade by the time the animal is one year old , changing to mottled gray and cream and eventually giving way to blue as adults . The adult blue iguana is typically dark gray matching the karst rock of its landscape . The animal changes its color to blue when it is in the presence of other iguanas to signal and establish territory . The blue color is more pronounced in males of the species . Their distinctive black feet stand in contrast to their lighter overall body color . 
