Mood rings are worn to theoretically display the mood or temperament of the person wearing it. They are made of thermotropic liquid crystals which are, essentially, liquid crystal molecules that react to a change in body temperature. When there's a change in temperature, these molecules move around and reflect and absorb different color wavelengths. While mood ring colors can't predict one's mood, they can provide a very vague indication of the way a person might be feeling.
The connection between body temperature and mood isn't particularly strong, however, so the colors of a ring won't always reflect the wearer's real mood. Additionally, the weather can affect the color displayed on a mood ring irrespective of the wearer's mood. A hot day can heat up the mood ring, for example.
The mood ring colors range the entire color spectrum, but a few colors come up more often than others. The first is black, which is generally the color the ring will be when no one is wearing it. It can also mean that the wearer is exceptionally tense, stressed, or overworked, however. Gray is rarely seen, but it can mean that the person is nervous, anxious, or sad.
Green is considered the most neutral of the colors. It is generally taken to mean that the wearer is in an average, normal state of mind; is relatively at peace and is feeling calm. It is more or less the "ideal" of the colors.
The blues are often taken to mean that the wearer is relaxed, happy, or emotional. Dark blue can sometimes indicate passion or love. These tones can also indicate an extremely peaceful state of mind.
The warmer mood ring colors can indicate a more enthusiastic state of mind. Amber can indicate mixed emotions, whereas yellow symbolizes an imaginative state of mind, or possibly boredom. Oranges and reds signify excitement; an adventurous, restless state; or even impatience and aggressiveness.
A pink color can demonstrate fear and uncertainty, or it can mean that the wearer is mellow and happy. A dark purple color nearly always signifies a sensual feeling, or romantic love. It can also indicate moodiness.
Going through these colors, it's clear that there is a good deal of similarity among their associated meanings. These rings and their meanings should not be taken too seriously, but they are often fun to consider. Mood rings can usually be purchased for a relatively inexpensive price at many toy and discount stores.