How can I make a section of an object react to my mouse being on it or my mouse clicking on it?

How can I make a section of an object react to my mouse being on it or my mouse clicking on it?

The object is basically an obj of a human and I want to make it so that when your mouse goes across it or you click it, that section of the body changes colour, as if it's 'heating up'. Think heat-sensitive clothing, like that.

This is for a college project so hopefully someone can help soon. Thanks in advance.