The ground-colour is generally a light brownish olive, but the lizard can change it to bright red, to black, and to a mixture of both. This change is sometimes confined to the head, at other times diffused over the whole body and tail. A common state in which it may be seen (as stated by Mr. Jerdon) is, seated on a hedge or bush, with the tail and limbs black, head and neck yellow picked out with red, and the rest of the body red. Jerdon and Blyth agree that these bright, changeable colours are peculiar to the male during the breeding-season, which falls in the months of May and June.
Mouhot has collected in Siam one of those fine variations of colours, which, however, appear to be infinite. It has the usual cross streaks between the eyes and the radiating lines continent of India to China; it is very common in Ceylon, not extending into the temperate zone of the Himalayas. Ceylonese specimens are generally somewhat larger; one of them measured 16 inches, the tail taking 11 inches. It is found in hedges and trees; it is known in Ceylon under the name of "Bloodsucker", a designation the origin of which cannot be satisfactorily traced; in the opinion of Kelaart, the name was given to it from the occasional reddish hue of the throat and neck. The female lays from five to sixteen soft oval eggs, about 5/8ths of an inch long, in hollows of trees, or in holes in the soil which they have burrowed, afterward covering them up. The young appear in about eight or nine weeks. In a hot sunny day a solitary Bloodsucker may be seen on a twig or on a wall, basking in the sun, with mouth wide open. After a shower of rain numbers of them arc seen to come down on the ground and pick up the larva and small insects which fall from the trees during the showers.
During the breeding season, the male's head and shoulders turns bright orange to crimson and his throat black. Males also turn red-headed after a successful battle with rivals. Thus their other gruesome name of "Bloodsucker Lizard". But they don't actually suck anybody's blood! Both males and females have a crest from the head to nearly the tail, hence their other common name "Crested Tree Lizard".
Changeable Lizards are related to iguanas (which are found only in the New World). Unlike other lizards, they do not drop their tails (autotomy), and their tails can be very long, stiff and pointy. Like other reptiles, they shed their skins. Like chameleons, Changeable Lizards can move each of their eyes in different directions.