Aura (Colour).

The colour theme of Sailor Mars is quite clearly red. This is a rather obvious colour choice for Rei as the colour of Mars is red. Depending on where you look, the colour has some different meanings, but generally speaking the following associations are pretty common.

In colour psychology the colour red is frequently associated with heat, energy and blood. It also brings to mind passion and anger. Most of these motifs are easily associated with the soldier of war, the latter two being considerably more prominent in her anime depiction. It can also be used to symbolize courage, a trait that is certainly fitting for Sailor Mars.

A person with a Red Aura is generally described as being down to earth and practical, they are physical and sexual beings. People with auras of this colour can be said to be materialistic. Reds are rarely associated with spirituality, which makes this seem like perhaps not the best choice of shades for the priestess of a shrine. They are said to be passionate and courageous, however, which feels more fitting.

Red generally has positive connotations in Asia, brides in China traditionally wear red dresses. It can symbolize courage, honour and success. In the West, while not associated with brides it does tend to be linked with passions are courageous hardiness.

Red is a colour that is nearly always associated with fire, and more often than not the planet Mars. An emotionally intense colour, red is a colour for getting noticed. Something that Rei in the anime is more fond of than the more reserved and ladylike manga version.

All in all, while perhaps on some planes red is the ideal colour to represent Rei, especially on the grounds of her anime depiction the colour red is an unfitting character trait for her manga one. However, passion and courage are traits that are both connected to red and an ideal respresentation of Sailor Mars.