I had a mood ring, and it was my most prized treasure!! Let's see if I can remember the 'moods' offhand:
Blue=cool, very relaxed
Green=nervous+tense
Yellow=?/don't remember
Orange/Red=angry
Purple=sexy
^That was my rusty memory, anyway. From HowStuffWorks.com:
* 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