One of the natures of souls on Aarn is that they tend to give a somewhat flashy light show before the discharge of a spell or magical effect. This light show carries with it a consistent color from soul to soul, and while this color can shift slowly over time, or be a subtle gradient from one color to another, it tends to remain consistent in the same individual.
Each soul's individual color is called their "aura color" and someone's aura color has tended to carry with it certain connotations and stereotypes about that person's personality. These stereotypes are not as fixed and highly defined as, say, astrology, but the societal impact is similar. One's aura color is considered an important part of their identity, and some of the trends (in Cerenbaun society at least) for what colors mean what are as follows:
Dark colors, such as blacks, navy blues, royal purples, browns and deep greens are considered to belong to more somber, pragmatic and calmer individuals. People with these colors are considered to be in control of their emotions and their actions. The darker and less saturated the color, the more this is considered to be the case - up to a point.
Pastel colors are thought to belong to childish, innocent, trusting, light, fluffy and not very substantial individuals. People with pastel auras however tend to be creative, expressive, loyal, compassionate and trustworthy. In the case of a color such as tan, a combination of both the dark/desaturated and pastel colors exists, producing someone considered to be very "normal."
Completely desaturated colors, from black, to grays to white, do not happen often. People tend to think of those with these colors as being mentally unhealthy or unstable. Usually an aura becomes desaturated over time, as someone rejects their previous beliefs or personality. Sometimes this change can be for the better - usually it is not. Rarely there are those who are born with desaturated auras, and these individuals are considered very pure - either pure innocent, or purely psychotic and sociopathic.
Generally, a desaturated aura represents a disconnect from some emotional concern that used to help define that person's personality - an absence of this kind of connection from birth will either produce a surreal-behaving prophet or a complete and total whack-job.
Extremely saturated colors such as bright reds, yellows, intense greens, cyans or fuchsias are considered to be a sign of an excess amount of magical energy, and the personalities of people with these colors are similarly expected to be quite intense exaggerations of the normal color stereotypes.
Across the spectrum, individual color shades are thought to have their own meanings, that can shift slightly from culture to culture, but generally follow the same guidelines.
Reds and oranges tend to be passionate and thrill-seekers. They enjoy the material world, and all it has to offer. As auras shift to golds and yellows, they tend to represent a playfulness in the case of yellows, or a nobility of spirit in the case of golds.
Greens tend to be ambitious and highly focussed individuals, while the shift through cyan to blue brings with it a sensitivity to healing and emotional concerns, with a value for love and the well-being of others. Violets, purples and indigos tend to be more spiritual, imaginative and fanciful, and a great many leaders and changers of the world have had auras in the upper spectrum.
Of course, one's aura color doesn't define one's personality. The patterns of behavior mentioned above are just that - patterns noticed by society. The paradigms of how certain colored auras are "supposed to behave" can help subtly mold one's personality while growing up, and many people rebel against these conceptions, refusing to be defined by the color of their magic.