What makes a mood ring change colors?

I don't know how to explain. But the color always matches my mood. Those are some cool chemicals.What makes a mood ring change colors?
it changes depending on your body temperature

your temperature slightly changes depending on your mood, which is reflected in the colour of the ringWhat makes a mood ring change colors?
Mood rings can't tell your emotional state with any degree of accuracy, but the crystals were calibrated with have a pleasing blue or green color at the average person's normal resting peripheral temperature of 82掳F (28掳C). As peripheral body temperature increases, which it does in response to passion and happiness, the crystals twist to reflect blue. When you are excited or stressed, blood flow is directed away from the skin and more toward the internal organs, cooling the fingers, causing the crystals to twist the other direction, to reflect more yellow. In cold weather, or if the ring was damaged, the stone would be dark gray or black and unresponsive.
skin temperature
Believe it or not, your body temperature slightly increases/decreases depending on your mood. Say you're angry/upset. Your body temperature increases slightly. The opposite is true if you're calm and relaxed.