Also referred to as thermochromic paint, heat-sensitive paint contains pigments that change color according to changes in the surrounding temperature. There are two main types of these pigments: leuco dyes and thermochromatic liquid crystals.
A paint that is sensitive to changes in temperature. Heat-sensitive paint is used in a variety of things, including mugs, baby bottles, kettles, car engines and much more.
Thermochromism is the property of certain materials to change their own color in response to a change in temperature. Thermochromism actually lies under the umbrella of a chemical phenomenon called chromism; a process that causes color changes.
Change is usually reversible in nature, meaning they can regain their original color in certain materials.
Thermochromic dyes are made from mixtures of leuco dyes and other suitable chemicals. The color changes that you see are basically the leuco dyes changing form from being colored to colorless (or transparent).
Source = "DIYlover"
All you have to do is get a cup, paint which sticks on porcelain and some heat sensitive pigment; which you can buy easily online. After making sure that you have all that is needed to make a colour changing mug, you need to follow these steps:
1. Cut out a pattern or picture that you’d like to paint on the mug.
2. Trace that pattern on the mug.
3. Paint it with the colour of your choice
4. After letting the paint dry, apply two thin layers of the heat sensitive pigment. Let it Dry.