Dungeon Keeper Ami features Jadite and Ami, occasionally. Jadeite also fills the same role to Cathy. On the other hand, Tiger is a red oni to everyone, even Jadeite.
Evangelion 303: Asuka is the Red Oni -she is hot-tempered, hot-headed, loud, boisterous, proud and impulsive-, and Shinji is the Blue Oni -calm, modest, quiet, patient, wary, understanding-. They are a Battle Couple.
In the Great Chicken Miasma's Mario fanfic Better Off Alone, the young Yoshi Waffles is the Red to everyone else in the group's Blue.
The dynamic between Chaos and Takato in the Tamers Forever Series is an interesting inversion of this trope. ChaosGallantmon has blue highlights on his armour, while Gallantmon has red highlights, and Chaos is also much more ruthless than Takato, but surprisingly enough, Takato is actually the Blue Oni, being much more subtle and thoughtful than the impulsive Chaos.
Peace Forged in Fire plays this contrast between Rahaen'Enriov D'trel ir'Aehallhah t'Rihannsu and Khre'Riov Morgaiah "Morgan" ir'Sheratan t'Thavrau, the two lead members of the Romulan Republic diplomatic team. D'trel doesn't like Velal, the Praetor of the Romulan Star Empire, and has diametrically opposed political views, and runs on Unstoppable Rage in battle, while Morgan is a more traditionalist Romulan, shares a friendly drink with Velal to hold the negotiations together, and has a much calmer, more rational fighting style. Also visible in their ship choices: D'trel's Kholhr is a Glass Cannon/Fragile SpeedsterT'varo-class light warbird, while Morgan captains a Mighty GlacierD'deridex-class battlecruiser.