Have you ever heard of mood rings? A mood ring is a ring that contains a thermochromic ingredient, for instance liquid crystal. The ring modifies color in reaction to the body temperature of its wearer. The color is said, by some promoters, to specify the emotional condition of the user. Invented in 1975 by Josh Reynolds and Maris Ambats, the rings are liquid crystals bonded with quartz stones.The hypothesis behind the thought that the ring shows the wearer's mood is based on a state that body heat changes with the emotional state of the wearer. Human body temperatures are known to fluctuate by small amounts (less than 0.5°C).
Deviations in ambient air temperature seem to have a bigger consequence on the temperature of the ring than changes in the body temperature of the wearer. No direct connection between a particular mood and a specific color has ever been validated.
Look at the Mood Ring colors listed below:
Dark blue: Happy, romantic or passionate
Blue: Calm or relaxed
Blue-green: Somewhat relaxed
Green: Normal or average
Amber: A little nervous or anxious
Gray: Very nervous or anxious
Black: Stressed, tense or feeling harried
Source:howstuffworks.com, wikipedia