Hello,
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.
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.
Darker raised areas can also be a result of fungal infections.
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