An anime, manga, and Japanese video game specific trope that's related to Colour-Coded for Your Convenience
. I'm not sure if we might add another section onto there, (although since this isn't specifically good vs evil, it might need too much explaining), or go with a new trope.
Oni is a Japanese word which loosely translates as demon or ogre, and represents a creature from Japanese mythology. The original oni were large, brutish creatures, often seen wielding large metallic clubs, Those that weren't in hell tormenting sinners roamed the remote, mountainous areas of Japan, and they often carried people off to be eaten, only to be defeated by valiant heroes. Later however they gathered other meanings, including as guardians of people or towns, which would mount oni figures on the walls to ward off evil spirits, (much like gargoyles in The West), and parades and processions would be led by men dressed as oni.
Differing sets of personalities are attributed to red oni and blue oni, which have come to be often come to be the personalities of many a protagonist/antagonist combination, or that of a pair of rivals.
The red oni is associated with passion, wildness, defiance and fire. A red oni character is often not too bright, but enthusiastic, determined, and filled with a zest for life. Often an Idiot Hero
or, in more mature pieces, a cousin of The Toblerone
. When a villain a red oni may turn into a Blood Knight
The blue oni is an opposite in most ways, more intellectual, traditional, cultured, spiritual and associated with water. Blue oni personalities are often respected but likely to puzzle or confound their peers because they are difficult to read and have a mysterious quality to them. Often The Stoic
or The Quiet One
. When a villain a blue oni's personality is often cold and ruthless, ready to do or sacrifice anything to accomplish their goal.
Jin and Mugen from Samurai Champloo
are not only prime examples of this, but also are always dressed in colors that reflect it too. They're also something of a deconstruction: Mugen is full of energy and reckless passion without direction or purpose, while Jin is practically unable to feel passionate about anything or form attachments to anyone.
Kazuma and Ryuho from the S-Cry-ed anime.
Inuyasha and Sesshomaru from InuYasha
Ken and Ryu from Street Fighter
are an arguable case.
Another arguable case is Ogami Itto and Yagyu Retsudo from Lone Wolf and Cub
. Although Itto doesn't have the not so bright or tasteless qualities of a red oni, he is driven to incredibly reckless behavior and horrid deeds by a passion for revenge, while Retsudo and the Yagyu are called the pillar of the shogunate by the shogun himself, and sacrifices an appalling amount of men and his own children in his attempts to stop Itto.
L and Light/Kira from the Death Note
anime series are often shaded or associated in red or blue to reflect this, although personality wise it doesn't quite apply. (Unless Light's God complex and obsession with "justice" count).
Goku and Vegeta of Dragon Ball Z
Naruto and Sasuke of Naruto. (Complete with the colors of their clothing and demon forms).
In the third Tenchu game, the evil wizard Tenrai employs both blue and red demons as foot soldiers. They're not given much personality, but the blue ones will make a suicide attack on you with explosives if you're spotted and their health is low.
There are numerous cases that could be argued from Bleach. Ichigo, Renji, and Kenpachi and others are all good cases for red oni, while Byakuya is a classic blue oni.
In the second Onimusha game, the always drinking, eating, and lecherous Ekei can pass for a red oni, while the serious, book loving, thoughtful Magoichi is a blue oni.
A non Japanese example: in the movie version of LA Confidential Edmund Exley is a near perfect example of a blue oni, (and nearly always dresses in a blue suit to boot) while Bud White is very much a red oni. (Complete with brown/maroon suit).