Under most systems for determining mood from a mood ring's color, blue is considered to mean that the wearer is relaxed and happy. Indigo and shades of blue close to it indicate that the wearer is in a loving mood, feeling spiritual or deeply calm.
Interpreting a mood ring is not an exact science, as colors and interpretation systems both vary. Under one system, dark blue is counted as a variant of the blue moods, but under others it is considered a variant of indigo. Blue is generally considered a positive color, and dark blue is often considered a more intense version of whatever mood blue represents in that interpretation system. Although blue and dark blue are most often said to represent calm, scientifically speaking, the opposite is true. Mood rings change color based upon the warmth of blood flow to the fingers. When people are excited, more blood flows to the extremities, releasing more heat and making the mood ring change color toward the blue and violet end of the spectrum.