Most Chameleons have prehensile tail, which basically means that the tail allows the creature to hold onto branches and move from one branch to another, in order to make its life easier when it is above the ground. In fact, the meaning of “prehensile” is ‘able to grasp’ (Prehensile tail, Wikipedia).
Since the creature has prehensile tail, the tail cannot fall off and then re-
As far as colour of tail is concerned, it depends on the Chameleon. Moreover, since the creature is able to change its skin colour based on temperature, light and mood, the tail colour changes to suit.
We have noticed that when a Chameleon is about to go to sleep, it curls its tail, whether this is to make the Chameleon appear smaller and compact keeping it better hidden or it could be simply that it’s the most comfortable position for the Chameleon to sleep in, we are not sure.
1) Main image supplied by Cow Yeow