The predominant color of green iguanas is green, but can actually range from brilliant green to a pale blue-gray. There are genetic variations in the color of iguanas. Some can appear more brown in color, while others are almost a turquoise blue. Recently, albino iguanas have been bred in captivity. One strain of green iguana from South America has a reddish cast to the head.
Young iguanas are generally brighter green or blue with some dark brown striping on the body and tail. The striping pattern of some actually results in a reticulated pattern. This coloring helps to camouflage them as they live among the bright leaves in their natural habitat. As they age, the green color becomes less intense. The dark patterns, striping, or banding on their bodies and tails become more intense as the iguana reaches approximately 18 months of age. The heads of older iguanas tend to be paler, appearing gray or almost white, as seen in the iguana on the left.
Breeding season and dominance
Male iguanas develop an orange to orange-red coloring as breeding season approaches. In some iguanas, the orange color may be diffuse over the entire body. In others, the orange can be concentrated in several areas including the dewlap, spikes, body, and legs. Female iguanas can also develop this orange coloration, though it is usually less intense.
Dominant males and females often retain the orange color past the breeding season. The orange color will persist if there are other iguanas present, or even dogs, cats, and people, over whom the iguana feels dominant.
Environment, especially temperature can influence the color of an iguana. Iguanas tend to become darker if they are cold. The darker color helps them absorb more heat. Color change in response to temperature is called "physiological thermoregulation." In addition to the darker color, an iguana may develop dark, wavy lines on its head or body if it becomes chilled.
Iguanas kept in too warm of an environment may become lighter in color.
Several weeks prior to shedding, an iguana's skin may appear dull and take on a gray or yellowish-gray cast. Unlike snakes, iguanas, and other lizards do not shed the skin over their entire surface at one time. White patches will appear where the skin loosens, just prior to being shed.
Iguanas with liver disease may appear yellow, especially their mucous membranes. This yellow color should not be confused with the yellow cast that may appear prior to shedding.
Red mite infestations may cause some scales on the skin to become raised and black. These are generally found on the ventral abdomen (belly) and limbs, and should not be confused with the normal striping or reticulated pattern. Darker raised areas can also be a result of fungal infections.
The skin over injuries will usually appear pink, smooth, and scaleless. Burns often appear black. With each shed, the affected area will become smaller. The new scales may be smaller and darker in color than neighboring scales.
Bacterial infections of the skin, often termed "blister disease," "scale rot," or "vesicular dermatitis," can at first cause blisters of the skin, and then turn the skin a dark brown to black color. These infections are usually due to poor cage hygiene or too moist an environment. This disease can be fatal.
Heavy parasite infestations, gastrointestinal obstructions or constipation, malnutrition, and other chronic diseases can cause an iguana to become mustard yellow to dark brown or almost black in color. These color changes generally affect the body and head first, then extend to the limbs and tail.
These color changes can also occur due to other stressors such as:
Poor environment (wrong temperature, humidity, photoperiod, inadequate enclosure, poor hygiene)
Fear resulting from a dominant cage mate, household pet, or person
Changes in household routine such as what may occur with moving, addition of new pets or a baby, holiday festivities, or long absences
Any color changes in your iguana, not related to breeding season or shedding, are an indication that your iguana may be ill and should be examined by a veterinarian.