Adventure Time: Their color scheme is backwards though: Marceline is a mischievous, loud, and careless Red Oni who has a bluish complexion (although she does wear red, which is weird since she eats red) while Princess Bubblegum is a polite, calm, and caring Blue Oni who is pink and wears a lot of pink (she is made out of bubblegum after all).
Zig-Zagged with Finn and Jake. In earlier episodes, Finn was the Hot-Blooded and headstrong Red Oni who relies on force and charges in headfirst and Jake is the wise and reasoning Blue Oni. Later episodes depicted Jake as the mischievous and bone-headed Red and Finn as a good natured and friendly Blue.
Trevor and Aeon from Æon Flux. Subverted, in that Aeon, despite being a cool, calculating, cause-oriented Blue Oni, is meant to represent chaos and anarchy, whereas Trevor, the vain, arrogant, people-oriented Red Oni, represents order and stability.
Aladdin: The Series: Aladdin: red/purple and white, uses his own strength, lives with a mess of friends, has a monkey sidekick, versus Mozenrath: dark blue and black, uses magic, lives alone in a ghost city, has an eel sidekick.
The Amazing Chan and the Chan Clan has two examples, one with an inversion in color: Sweet-tempered Suzie wears blue while boisterous tomboy Anne has a lot of orange in her outfit, but responsible Henry wears orange while impulsive goofball Stanley wears blue and green.
Inverted example: Gumball is impulsive, passionate and reckless, while his brother Darwin is naïve, cautious and calm, although Gumball's fur is blue and Darwin's scale is orange (close to red).
Their sister, Anais is usually the voice of reason in family. And despite being the youngest member of the family, she is the most intelligent, experienced and cautious one.
Gumball's mother, Nicole is very ill-tempered, mature and strict, while Richard, Gumball's father, is laid-back and calm. Ironically since Nicole's fur is blue while Richard's is pink (close to red).
Dagget (red oni) from The Angry Beavers is highly emotional and prone to Donald Duck-esque rages; stark contrast to his older brother, Norbert (blue oni), who is cool-headed and considers himself suave.
Probably the most clear cut case for this in actual characters is the contrast of angry, defiant Determinator Zuko, who lives and dies with the Indy Ploy (although he is by far one of most complex reds), and the Chessmaster/Dragon Azula, who even makes blue fire (which is actually hotter). Some other notable examples of playing with red vs blue include:
Zuko's Dream Sequence, where his Uncle Iroh is represented by a red dragon and Azula by a blue one.
Best friends turned enemies Avatar Roku and Firelord Sozin both had dragon companions. Roku's was red, Sozin's blue. Sozin tricks Roku, leaving him to his death.
Zuko also plays Red Oni to every one of Team Avatar's Blue Oni's (except for Toph).
Aang and Zuko are taught a different version of Firebending philosophy, formed, at least in part, by a red and blue dragon. Zuko is being taught to move beyond destructive motivations (his red oni background) while Aang is being taught to accept his destructive potential (against his blue oni background). Also the contrast in their facial markings. Zuko's Red Scar and Aang's Blue Tattoos.
Zuko and Katara in general. Zuko is angry and passionate while Katara is caring and nurturing, however in the interactions between just the two of them, they switch roles. Katara is constantly angry and emotional and extremely protective of Aang and her own interests. Zuko is calm and thinks about how to deal with her. Furthermore, Katara is typically dressed in blue and Zuko in red.
Except, of course, in each of their 'spirit' alter-egoes: the Blue Spirit and Katara's reddish Painted Lady. In that commonality, their color schemes reverse.
During the Boiling Rock infiltration Sokka was the Blue Oni, A non bender Water Tribesmen strategist and The Leader vs Zuko's Red, a Firebending Fire Nation fighter and The Lancer.
Zuko and Azula end up switching during the Grand Finale: Zuko, having been trained extensively in discipline and control of his strikes from Iroh, takes up the role of Blue during his final duel with Azula, while Azula embraces Red as a result of her Sanity Slippage and flies off the handle with wild and powerful strikes.
Aang is, appropriately enough, a combination of the two. Aang normally can be both foolish and passionate (represented by his normal saffron clothes and temporary Fire Nation wardrobe change, which he later salvages to make a new set of robes). But when in his glowing blue Avatar State, Aang can become frighteningly cold and ruthless, to the point where Aang himself has nightmares about it.
Katara and Sokka are a zigzagged example. When it comes to focusing on the mission and long-term goal, Katara tends to act on instinct and let her Chronic Hero Syndrome get the better of her whenever there's something she sees the need to attend to, while Sokka remains firmly focused on reaching the ultimate goal and generally tries not to distract himself too much with any side-quests like his sister does. However, in more general casual situations, Sokka is often a zany, eccentric goofball who consistently cracks jokes, while Katara is the mature and patient Team Mom of the group who acts as the Only Sane Woman whenever the others' vices get the better of them.
More broadly, this applies to the Fire Nation and Water Tribe. Fire Nation are typically dressed in red (and black) compared to the Water Tribe, who are typically dressed in blue (and white or gray). Firebeinding is offensive, Waterbending is mostly defensive.
In terms of personality this is inverted in the case of the vastly giftedmotherless young daughters of important leaders on the opposing sides. Katara a passionate and somewhat impulsive Team Mom whose will sabotage her own plans to help people in need, while Azula is a calculating manipulator who has a hard time dealing with people on a personal level at all.
The Siege of the North — the Fire Nation troops are the aggressive attackers whose deluded military leaders (General Zhao and Prince Zuko) are busy with insane schemes (to kill the Moon spirit and capture the Avatar respectively). Meanwhile, the Northern Water Tribe are defending themselves, planning to infiltrate the Fire Nation navy]] and seek help from the spirit world. The color scheme throughout those episodes fits this trope to a t — the moon and night sky become blood red when the Fire Nation Admiral Zhao begins to kill the Moon Spirit, foolishly risking the destruction of the earth in order to prevent water benders from bending, thereby making the city an easy target. The response from the Northern Water Tribe is exceptionally non-aggressive, as the princess, something of an incarnate of the Moon Spirit, sacrifices her mortal life with the aim of restoring balance to the world and enabling others to fight against Fire Nation imperialism.
Also, the (red) Fire Nation and the (green, not blue) Earth Kingdom during the attacks and sieges of Ba Sing Se and the establishment of Fire Nation colonies, where the Fire Nation are pretty clearly the (unsustainably) aggressive party. Of course, the Earth Kingdom has the Dai Li, who dress in cooler colors and engage in more underhanded aggression, like brainwashing.
Its sequel series, The Legend of Korra, features hero Korra and her lancer Mako who also double as the Official Couple (for the first two seasons anyway) as this trope. Their Chromatic Arrangement is the opposite of their oni; Korra, the Avatar, is a hotheaded native waterbender, and Mako is a cool and controlled firebender.
Korra is also the brash, rough-and-rumble Red Oni to Asami's calm and elegant blue. Just like with Korra and Mako, their Chromatic Arrangement is the opposite of their oni, with Asami consistently dressing in red and Korra primarily dressing in blue. They also double as the Official Couple at the series finale.
In Season 2, loudmouth inventor/socialite Varrick and his quiet assistant Zhu Li played very straightly. Also Desna and Eska count, Eska becomes a rather terrifying Red (matching or even more scarier than Azula), while Desna plays a submissive and somewhat more understanding Blue twin.
Outside of battle, red-clad Iron Man often acts more brash and short-tempered than the calm, reflective, and blue-clad Captain America.
For most of the first season, The Wasp loves the exciting and beneficial qualities of crimefighting, but her colleague, Ant-Man (whose red costume seems ironic in this case), prefers to confront criminals by talking things out and rehabilitating them. They switch roles during scientific projects, which Ant-Man enjoys more than Wasp does.
One of Wasp's friends, red-clad Ms. Marvel, confronts invaders with violence while Ms. Marvel's blue-skinned alien protector, Captain Mar-Vell, believes in finding peaceful resolutions. Their first appearance, as ordinary Army majors, contained another visual metaphor: Ms. Marvel wore a red scarf and Mar-Vell (disguised as an earthling) wore a blue suit.
The Heroes For Hire include hot-blooded Luke Cage and restrained Iron Fist. Their different temperaments get lampshaded while Iron Fist meditates.
Inverted with Pablo and Tyrone of The Backyardigans: Pablo's blue, hot headed, and panicked a lot in Season 1, placing him as the Red Oni. Orange-furred Tyrone, on the other hand, is calmer and more level-headed, which are true aspects of a Blue Oni.
Out of the stretchy superheroes in Batman: The Brave and the Bold, Plastic Man, who wears red, is much more blunt and okay with stealing valuables from the scene of the crime, while Elongated Man, who wears purple (it's a kind of blue) is much more analytical and noble. Plas has a similar dynamic with Batman himself.
Pretty much any of the other heroes are this when paired up with the boisterous and foolhardy Aquaman.
Beavis And Butthead. While both of the boys are active pranksters and neither of them show good judgement, Beavis is Hot-Blooded, brash, irritable, and violent, while Butthead is more laid-back, calmer, and (barely) smarter. Ironically, Beavis wears a blue shirt while Butthead wears red shorts.
In Beverly Hills Teens, Larke is the calm and laid-back blue oni, and Bianca, while more prim and proper than Larke, is the shorter tempered and irritable red oni.
In Bonkers, Bonkers (red) and detectives Lucky Piquel and Miranda (blue).
The Boondocks: Huey Freeman is a blue oni in the Ryu mould (reserved and scholarly whilst holding radical political views with great passion) while his brother Riley is a Ken-style red oni (loud and charismatic but in his own way much more of a people person).
Chip 'n Dale: Rescue Rangers: Dale, with his fun-loving nature and tendency to goof around, is a red oni. Chip, on the other hand, is much more serious and hard-working, making him a blue oni.
Class of 3000 has Li'l D and Philly Phil. The former is more impulsive, a bit rude, and more likely to take charge, while the latter is more easygoing and more of a follower. Ironically, Li'l D has the cool color palette (green shirt and blue pants), while Phil's the one with the warm palette (yellow clothes and red hair).
Played with slightly in Season 2, where Phil's a bit more emotional.
Ed, Edd n Eddy: Eddy is short-tempered, has No Indoor Voice, hates following the rules, and follows his gut (Red Oni) while Edd (Double D) is willing to follow the rules, intelligent, rational, and thinks before he acts (Blue Oni).
Eds (relatively nice guys, trying to succeed via cunning rather than brute force) are blue to the Kankers' (blunt, insensitive molesters, always solving their problems by violence) red.
Family Guy: Stewie is red to Brian's blue, and Peter is red to Lois' blue. Other pairings within the family can be all over the place, but Brian is definitely the bluest overall. Among the guys, Cleveland is probably the bluest, Joe is generally blue but can get REAL RED REAL FAST AND REAL LOUDLY, Quagmire is usually red, and Peter is almost always red.
Foster's Home for Imaginary Friends: Bloo (red oni) is obnoxious, self-centered, and rude, while Mac (blue oni) is intelligent, shy, and always wants to do the right thing (most of the time). Ironically, Bloo is well, blue, while Mac wears a red T-shirt.
Freakazoid and Cosgrove in Freakazoid!. In the episode "Two Against Freak", RoddyMacStew fills in as the Red Oni while Freakazoid is in the hospital. They're even — albeit unintentionally — in the right colors: Freakazoid's in red tights and Roddy's kilt is red, while Cosgrove is always in his blue police uniform.
Futurama has Fry (blue) and Bender (red). Bender is shown to be insensitive, reckless, and inconsiderate of others while Fry is more laid back, softer spoken, and more kind of the two. Ironically, Fry is a redhead who wears a red shirt while Bender is a grayish-blue robot.
Fry (red) and Leela (blue). Fry is a simpleminded, impulsive, hyperactive Manchild who often ignores the responsibilities of his job thanks to a short attention span and sheer laziness, while Leela is a mature, intelligent, somewhat stoic space captain whose dedicated to the job, prioritizing the rules and punishing Fry and Bender whenever they don't follow orders. Blurring the lines a little is that Leela and Fry are a Masculine Girl, Feminine Boy pair, with Leela being a highly efficient Action Girl with Blood Knight tendencies and Fry being a Cowardly Lion whose more likely to hide behind her and scream in dangerous situations. Though he does step up when the situation calls for it.
Zapp Brannigan (red) and Kif (blue). Zapp is very arrogant, egotistical, perverted, narcissistic, and is very abusive towards Kif while Kif is more softer spoken, sensitive, shy, and more passionate. Ironically, both of them wear red suits.
Hermes (red) and Zoidberg (blue). Hermes is very hard working but is very condescending, rude, spiteful toward people like Zoidberg while Zoidberg is more kind, sensitive, and childish. Ironically, Zoidberg wears a red shell.
In "T: The Terrestrial", Lrrr (red) and Jrrr (blue). Lrrr is more hot headed, loud, self centered, and more willing to invade planets and hurt humans while Jrrr is more sensitive, sweet, kind, and does not want to hurt humans. The fact that Jrrr is Lrrr's son is what connects them together to this trope and Lrrr wears a red cape while Jrrr wears a blue cape.
It is also known that calm, and cool Wendy is Blue oni to Mabel's and Soos's Red.
Grenda is the Red Oni to Candy's Blue.
In the cartoons series for Disney's Hercules, Ares the God of war and Athena the Goddess of wisdom, who were siblings and rivals, were perfect representations of this trope. The crossover between Aladdin has Jafar and Hades under these with their colors.
Helga Pataki from Hey Arnold! is an aggressive and hot-tempered red, her best friend Phoebe Heyerdahl is an intelligent and laid-back blue.
Gir seems to show some signs of this trope, though the colors are reversed. The first few seconds when he was active, the episode "Gir goes Crazy and Stuff", and occasionally through-out the series, Gir's colors switch from blue to red and back again. When red, he seems to show the traits of the Blue oni and is intelligent, calm, and eager to serve his master (often saying "Yes my Master!"). When Blue, he acts more like the Red Oni and is wild and over the top, with no control over his own urges or actions.
There is also the scene were Zim hypnotises Dib and the scene shows the ground falling apart with Zim in red and Dib in blue. Makes sense, since Zim is known for being impulsive and not thinking before acting, where as Dib is more scientific and logical (if only by a little bit).
Jackie Chan Adventures has Jade being all impulsive, insistent, and violent while Jackie is relaxed, thoughtful, and peaceful.
Johnny Test has Johnny (red) and his dog Dukey (blue). Johnny is shown to be very reckless, bratty, and more willing to abuse his sister's experiments while Dukey is more sensitive, cautious, and is more willing to warn Johnny of the consequences of his actions
Susan (red) and Mary (blue), Johnny's twin sisters. Susan is more hot tempered of the twins while Mary is more calmer but firmly strict. Ironically, Susan wears a blue shirt while Mary wears a yellow shirt in most of their screen time.
In Justice League, Hawk and Dove, who are also brothers, then one brother and a girl, then two girls, according to the DC Encyclopedia.
Henry is the red oni (he's energetic, idiotic (not to extreme levels)), while June is the blue oni (cool, cynical, smart). With June, it kind of makes some sense: she does have blue hair, after all. Ironically, Henry wears a blue shirt, where as June wears a red jacket.
In Life with Loopy, Loopy is the red oni (energetic, life-loving) to her older brother Larry's blue oni (inteligent, shy). Oddly enough, the colors of their hair are the opposite (Loopy has blue hair, Larry has red).
King of the Hill: Dale and Bill are generally the red, Hank and Boomhauer the Blue. Though Hank is dedicated to the point of near-blindness and refuses to admit he has an anger problem
Legend Of The Dragon has the dragon twins Ling and Ang. You may think from looking at pictures that Ling is the blue Oni and Ang is the red Oni. However, in terms of personalities, Ling is the red Oni and Ang is the blue Oni.
In Looney Tunes, Daffy Duck serves as the hot-tempered, overacting, obnoxious red oni to Bugs Bunny, who is a calm, cool, intelligent blue oni. Bugs himself becomes the red oni when contrasted to Cecil Turtle the the Tortoise and Hare based cartoons.
The twins, Lana and Lola. In an interesting twist, however, the prim and proper, girly Lola is the red oni, while the dirty and rough Lana is the blue oni. Lola has a Hair-Trigger Temper and can be quite the manipulative psychopath on her worst days, while Lana is actually quite calm and relaxed, especially by the standards of the Loud siblings.
Of the youngest siblings, the near stoic, scientifically driven Lisa (blue) and the emotional baby Lily (red). Lisa also plays blue oni to her more socially outgoing friend, Darcy.
Luan is the red oni to Lucy's blue oni. Both are interested in the performance arts, but Luan is a cheerful comedian while Lucy is a Goth.
Luna is also the red to Lucy's blue. Both wear dark clothing and have "edgy" fields of interest. But Luna is an energetic, aspiring rockstar, while Lucy is The Stoic and a gloomy goth girl.
Between the girliest sisters, hot-headed Lola is the red to Nice Girl Leni's blue. Similarly, on the tomboyish side, Competition Freak Lynn is the red to laid-back Lana's blue.
To a minor extent, Leni could be considered a red oni relative to Lori's blue out of the oldest sisters. Lori is more rational and level-headed (though she does have a bit of a temper at times, though nowhere near as bad as fellow girly girl Lola's), while Leni is less intelligent and can do some very silly things as a result of this.
Even though they've never interacted on-screen, the two rough and tough tomboys Lynn and Ronnie Anne fit this trope. Lynn (hyperactive, energetic, sports nut) is the red, Ronnie Anne (grouchy, snarky, irritable) is the blue. Furthermore, Lynn will often rely on her strength and brute force to solve a problem, while Ronnie Anne in spite of her roughness often resorts to scheming, plotting, cunning and trickery when faced with a challenge, similar to Lincoln.
Their methods of babysitting show this, too. Ronnie Anne was shown to be quite a nurturing caretaker for her and Lincoln's egg (not to mention Bobby and Maria) in "Shell Shock" while Lynn struggled with babysitting in "Sitting Bull" because she was too aggressive and destructive.
Mike, Lu & Og: Mike is the red oni to Og's blue oni, although she becomes a blue oni when contrasted with a certain green wearing island princess.
Mr. Bogus (red) and his best friend Tommy Anybody (blue). However, ironically enough, Bogus actually wears a pair of blue pants, while Tommy wears a pink shirt (to be completely fair it would be the closest thing to red) though he does wear blue jeans.
Earth ponies Pinkie Pie is an extreme Genki Girl and a Cloud Cuckoolander, compared to Applejack, who is down to earth and more straightforward.
Meanwhile, the pegasi Rainbow Dash is a mostly passionate and confident Tomboy to Fluttershy as the shyer and uncertain Girly Girl.
Turning to the unicorns, Rarity is prone to theatrics, often descending into Large Ham territory, which contrasts with Twilight Sparkle's more sensible and serious nature.
This is a list of the Mane Six (and Spike) by order of most red to most blue: Pinkie Pie, Rainbow Dash, Rarity, Spike, Applejack, Twilight Sparkle, and Fluttershy.
The Cutie Mark Crusaders count as well. Scootaloo being the Red Oni to Sweetie Belle's Blue Oni. Apple Bloom is either the Blue Oni to Scootaloo or Red Oni to Sweetie Belle.
Done with the Princesses, yet played unexpectedly. Analytical Celestia, the light-colored ruler of the Sun and Day, is the rational and wise blue oni, while intuitive Luna, the dark-colored ruler of the Moon and Night, is the quick-tempered and emotionally driven red oni. Inversed with their Evil Counterparts, Nightmare Moon (Luna) is pragmatic and Day Breaker (Celestia) is gleeful in the destruction she wreaks.
Hyperactive party pony Pinkie Pie is the Red to her quiet, rarely-emotional sister Maud and her bashful, even quieter twin sister Marble, but the Blue to her other sister, Limestone, who ranges from simply cranky to flat-out volatile.
In Over the Garden Wall older brother Wirt is an angsty, intellectual, chronic overthinker while his younger brother Greg is a loud, excitable doer.
Also seen with polite, soft-spoken rule-follower Wirt compared to foul-mouthed, scrappy, Fiery Redhead Beatrice.
Ozzy & Drix has this with a color inversion just like the movie it was based on, mentioned above, with Ozzy as the Red Oni and Drix as the Blue Oni. This is despite Ozzy being blue and Drix being red.
Phineas and Ferb, respectively. Phineas is the talkative extrovert, while Ferb is The Quiet One. Phineas also has red hair, while Ferb's is green.
Both brothers are the chilled out and laid back blue to Candace's ill-tempered, neurotic, obsessed red.
Candace is also the red to Stacy's blue. Candace is the paranoid, loud mouthed teen obsessed with busting her brothers, while Stacy is the Only Sane Man (or girl) who acts as the Voice of Reason. Fittingly, Candace wears a red tank top while Stacy wears a blue skirt.
Dr. Doofenshmirtz is the talkative, eccentric and theatrical red while Perry is the serious and silent blue.
Ready Jet Go!: Due to the depth of the characters and wide variety of character dynamics, this show has plenty.
The most obvious one: Jet is the Red Oni, Sean is the Blue Oni. Jet is hyperactive, leaps before he looks, and is very energetic and enthusiastic. Sean is more nervous, intellectual, and calm. During Sean's dream sequence in "Back to Bortron 7", Jet even stands in front of a red sphere and holds a pink one, while Sean stands in front of a blue one and holds a purple one. However, Jet can also be the Blue Oni to Sean's Red Oni, because Sean is more prone to panicking under pressure and being annoyed, than Jet is.
Jet could also be considered to the Red Oni to Sydney's Blue Oni.
Sean is the Red Oni to Sydney's Blue Oni. As stated before, Sean is more prone to freaking out and getting frustrated, unlike Sydney who has a level-headed, mellow nature. However, Sydney can also be the Red Oni to Sean's Blue Oni because Sydney is wildly imaginative and often goes along with major Red Oni Jet's ideas, while Sean often plays the role of the Only Sane Man.
Mitchell is the Red Oni to Jet's Blue Oni. Mitchell often gets irritated, while Jet is more optimistic and patient. Fittingly, the former wears red while the latter wears blue. Mitchell could also be seen as the Red Oni to Mindy and Lillian's Blue Onis because those two are also calmer than he is.
Mitchell is also the Blue Oni to Jet's Red Oni. Jet is super excitable and often leaps before looking. Mitchell, on the other hand, is calmer than he is and more pragmatic. He is also the Blue Oni to Mindy and Lillian's Red Onis because those two are very energetic.
Jet's cousin Zerk is the Red Oni to Jet's Blue Oni. Zerk takes Jet's Keet tendencies Up to Eleven and then some, while Jet is more responsible than him and tries to be patient with his antics.
Mr. Peterson is the Red Oni to Dr. Rafferty's Blue Oni. Mr. Peterson is shown to have a temper, if his extreme rage at the beginning of "What's a Satellite?" is any indication, and is a Large Ham at times. Dr. Rafferty, on the other hand, is usually easy-going and patient. This is best shown in "Mini-Golf at the DSA".
In the Disney Wartime Cartoon "Reason and Emotion", Reason is the blue to Emotion's red. They even happen to be colored blue and red. The cartoon also argues that Adolf Hitler destroys the blue and plays on the red to gain power.
Used a bit with the main six in Recess when broken into three groups of two:
T.J. as the red oni (hot-headed, easily excitable) with Vince as the blue oni (cool, sarcastic)
Spinelli as the red oni (hot-tempered, tough) with Gretchen as the blue oni (smart, laid back)
Mikey as the red oni (outgoing, drama king) with Gus as the blue oni (shy, quiet)
In Regular Show, Mordecai (blue) and Margaret (red) deliberately follow this trope — both in appearance and personality. To a greater extent, there's the relationships between Mordecai and Rigby, and the relationship between Muscle Man and High Five Ghost.
Ren & Stimpy: Ren (Red Oni) is often hot-headed, borderline psychopathic and unstable, while Stimpy (Blue Oni), as much as an "eediot" he is, is easily much more reserved and rational than Ren. Funnily enough, Stimpy is the blue oni despite being a red cat.
Sisters Emma and Kitty. Emma is the blue Oni as she is more cautious, intelligent, and more focused while Kitty is the red Oni as she is more fun loving, enthusiastic, and reckless.
Cadets MacArthur and Sanders. MacArthur is in the red due to her aggressive, reckless, and impulsive behavior while Sanders is in the blue as she is more cautious, is more willing to uphold the law and play fair, and tries to calm her racing partner down a lot. Ironically, they both wear blue clothing.
Jacques and Josee. Josee is in the red due to being very hot headed as she throws tantrums when she and Jacques place anywhere other than first and Jacques is in the blue as he constantly fears Josee's tantrums and constantly Screams Like a Little Girl.
Out of Rocko's friends, Heffer is fun-loving and brash (red) while Filburt is nerdy and introverted (blue).
The Bigheads are a good example. Ed Bighead is loud, short-tempered and spiteful (red) while Bev has a moral compass and doesn't have any resentment towards Rocko, Heffer or Filburt (blue)
Tommy and Chuckie from Rugrats are respectively Red and Blue — Tommy is the (red) fearless leader who loves adventure and mischief, and Chuckie is the (blue) "scaredy cat" who always warns his friends not to do what they're doing and tries to stay out of trouble. Ironically, Tommy wears a blue shirt, and Chuckie is a redhead.
Both played straight and inverted on Rupert: The protagonist Rupert Bear wears red and is an adventure-loving thrill seeker who's always eager to swing into action and come up with an Indy Ploy to save the day; his Lancer Bill Badger wears blue, is far more cynical and snarky, and is reluctantly dragged along on all the hero's adventures. In a twist, Rupert is definitely the more level-headed one, while Bill is more reckless and prone to acting without thinking. However you look at it, the two are opposites... and best friends.
One episode ("Alter Ego") of the 1970s Filmation Sabrina, Superwitch cartoon featured Dameana, a raven-haired Sabrina lookalike with a shrill, grating voice. Depending on whom you ask, Dameana is Sabrina's "magical mirror image," her alter ego, or merely her cousin, but what is clear is that she and Sabrina are literal examples of the trope; the rowdy and rambunctious Dameana wore a red dress, and the demure and proper Sabrina wore a blue dress.
Samurai Jack has Jack (Blue) and the Scotsman (Red). Jack is quiet, stoic, and relaxed; the Scotsman is loud, boisterous, and passionate.
In the 2017 continuation, Ashi acts is the determined Red oni to Jack's sullen Blue.
In Sidekick! Vanna while an Alpha Bitch, usually (When she isn't pissed off at Eric) hides her emotions and acts pretty chill most of the time (Blue) As opposed to Kitty who is extremely hyper and excitable (Red) as well as Eric is the rational Only Sane Man (Blue), while Trevor is impossibly impulsive and does literally everything he possibly can without thinking ahead (Red)
The Simpsons: The impulsive Homer is the Red Oni to the pragmatic, tradition-worshipping Marge's Blue Oni. Ironically, Marge is more strict than the laid-back Homer.
There's also Bart's red (hyperactive, mischievous and has a disdain for authority figures) to Lisa's blue (smart, good-natured and generally obedient).
Groundskeeper Willie has a Hair-Trigger Temper and shows resentment towards Skinner (red), while Principal Skinner is consistently shown as an Extreme Doormat towards Chalmers and his mother, and barely manages to keep the school open (blue).
Square One TV inverts this trope with their animated sketch series Zook & Alison, The boy, Zook, is loud, nervous, and outgoing, but is Blue in color, while his Pink sister, Alison, is calmer and smarter.
Although at first, Stan and Kyle had similar personalities, later on, they started to differentiate. Stan became an introverted and calm Deadpan Snarker, while Kyle became an impulsive, bold, and Hot-BloodedSnark Knight, especially in Cartman's presence. Bonus points for Stan always wearing a blue hat and Kyle always wearing an orange jacket along with having red hair.
Tweek and Craig fit this trope, as well. The former is hyperactive, paranoid, emotional, and anxious, while the latter is stoic, pragmatic, monotone, and snarky. Bonus points for Craig always wearing blue clothes.
Star Wars Rebels: Garazeb "Zeb" Orrelios is the Red to Agent Kallus' Blue. Zeb's the gung-ho, Proud Warrior Race Guy with a hot temper is on the side of the Rebels to Agent Kallus' calmer and more orderly, manipulative nature for the Empire. Both of them found mutual respect for one another based off their adherence to their honour code and Deadpan Snarker tendencies and the fact that Zeb saved Kallus' life when they were stranded on one of Geonosis' moons.
There's Hot-Blooded, cocky, casual Amethyst and precise, intelligent, sometimes inflexible Pearl. However, Pearl isn't as together as many a blue oni — her insecurities can lead her down the wrong path to a much larger degree than the typical red oni impulsivity of Amethyst. They're constantly arguing over how to do things, but can pull it together when they need to (if the emergency is big enough, or when leader Garnet has well and truly had it with their bickering, or, most of all, if Steven gives them that teary-eyed look.) You'd think they're as red and as blue as two characters can possibly get until we meet...
Ruby and Sapphire, the two Gems who fuse into Garnet. When forcibly separated and put into different prisons, Ruby is angry and nerve-wracked, going around screaming Sapphire's name as soon as she's freed; Sapphire, in contrast, calmly sings her in cell, and uses her freedom to quickly and efficiently hunt Ruby down so that they can fuse again. This extends to Personality Powers in "Keystone Motel", as the pair respectively become very hot and very cold — quiteliterally — when they're angry at each other. Keystone Motel also lets us get to know them better — Ruby's emotions are very much worn on her sleeve while Sapphire is outright The Spock. Believe it or not, their roles are reversed in "Now We're Only Falling Apart", as Sapphire (red) is absolutely livid at the revelation that Rose is Pink Diamond, whereas Ruby (blue) takes the revelation quite well.
The titular Steven is goofy, outgoing, and wears a red shirt, while his best friend Connie is more quiet, intellectual, and wears blue in the first intro and several episodes (for example, "Alone Together".)
Yellow Diamond, who has a volcanic temper, is the red to her 'sister' Blue Diamond's blue, as she is mostly melancholic these days. Their other 'sister', Pink Diamond, is the red to both Blue and Yellow's blue.
Fittingly, The Diamond's Pearls share a similar dynamic, with Yellow Pearl being presented as haughty, smug, and more emotional, while blue pearl is generally reserved and stoic even.
Super Noobs: Alien warriors Memnock (blue) and Zenblock (red). Zenblock is very hot tempered, impulsive, reckless, gruff, and often shouts at other peple a lot and he considers himself to be mean. Memnock on the other hand is more relaxed, sensitive, cautious, and is the most childish of the two. Ironically, Zenblock's skin color is blue while Memnock's is yellowish-green. Their different personalities often cause them to frequently clash at each other in terms of their ideals.
SWAT Kats: Chance 'T-Bone' Furlong and Jake 'Razor' Clawson. T-Bone is the Red Oni because he is the more aggressive type when it comes to his piloting skills in the air, and physical when it comes to fighting on the ground, while Razor is the Blue Oni, being the gadgeteer of the team who also serves as T-Bone's RIO (Radar Intercept Officer) when flying in the Turbokat. Then they're seen outside their vigilante and work clothes, they're wearing their respective colors.
In Taz-Mania the Taz/Dingo shorts, Taz plays the role of the Hot-Blooded red oni while Digeri Dingo plays the role of the cool and cunning blue oni. Also, Molly and Jake, with Molly being the easily-stressed red and Jake being the more cheerful blue.
Robin and Starfire are represented by Red and are more brash, stubborn, and passionate than the others (Starfire displays this most in the comics, to which the flashback/origin episode "Go" paid tribute).
Cyborg and Raven are represented by Blue and are more intelligent, analytical, and, in Raven's case, cold.
In the Teen Titans comic, Red Devil (literally a Red Oni) and Blue Beetle have become a comic relief dynamic duo that fans have dubbed Beevil. While both characters have similar personalities, Beetle tends to be level headed while Devil is more impulsive.
Slade is definitely the villainous Blue to Robin's heroic Red.
Thunder (blue) and Lightning (red). While both brothers start out as destructive forces, Lightning is the more boisterous and hot-headed of the two, while Thunder is more calm and contemplative, as well as the first to question the damage their "fun" brings.
Leonardo (blue) and Raphael (red). Reversal in that Leo is the leader of the team (aside from Splinter). Raph does the Blood Knight bit when he takes the guise of Nightwatcher in the CGI movie. It was noted with this exchange from the first episode of the '03 series:
Raph: Teacher's pet!
Leo: Ninja dropout!
Even the other two turtles, Donatello and Michelangelo, fit this trope. Michelangelo being the wild, extroverted, and more emotional Red to Donatello's calm, introverted, and more logical Blue.
In Thunderbirds Are Go Scott and Virgil Tracy are red and blue, respectively. Especially in the episodes "Crosscut" and "Recharge". Virgil also acts as the blue Oni to Gordon's red.
John acts as blue Oni to all the other Tracys (and EOS).
Tiny Toon Adventures has Buster who is the more intelligent and calm of the 2 stars as the Blue Oni, and Babs who is the more crazy and mischievous of the 2 stars as the Red Oni.
In Titan Maximum, the original Titan Force Five had the Hot-Blooded Palmer and his Lancer Gibbs (they even wear red and blue respectively). However, the fact that Gibbs was the Only Sane Man of the team (as well as Palmer leaving him to die just so he wouldn't miss a hot date) led to Gibbs turning evil in the first episode.
Gwuncan, also fits for this trope, as Duncan is a red oni, while Gwen is a blue oni.
Loud, fun-loving, impulsive, bone-headed, optimistic Owen (red oni) has an Odd Friendship with the quiet, anti-social, calculating, intelligent, gloomy (blue oni) Noah. Ironically, Owen wears a white t-shirt with a large blue maple leaf on it while Noah wears a red sweater vest.
An (almost) literal contrast in 80's animated film The Transformers: The Movie: Hot Rod, impulsive and flame-themed (well, his name is a hint), is red (in a color tone tending a bit to magenta). Kup, calmer and more experient, is greyish blue (or blueish gray).
Marvel Comics continuity in particular played up the contrast between Blue Oni Autobot leader Optimus Prime (calm, noble and rational) and Red Oni Dinobot (and sometimes all Autobots) leader Grimlock (impulsive, violent and bombastic).
Also in Transformers' eyes. The wild, violent Decepticon have red eyes; The good-hearted, rigtheous Autobots have blue eyes.
The two factions in general. The Decepticon's are the Red Oni dominated side (with a few Blue Oni exceptions like Soundwave), while the Autobot's are the Blue Oni opposites (with a few Red Oni exceptions like Jazz).
Blitzwing has a Split Personality represented by his three faces. The black face is The Mad Hatter, but the red and blue faces are textbook red and blue oni: the blue face is cold, calm, and calculating (and uses ice powers), while the red face is brash, impatient, and aggressive (and uses a flamethrower).
Even his alternate modes reflect this; the blue face wanted to choose a fighter jet, maneuverable and good for attacking from a distance, while the red face insisted on an assault tank, heavily armored and bristling with firepower, ideal for being right in the middle of the action. After they'd argued for a bit, the crazy face stepped in and, cackling madly, scanned both; which one he uses depends on which of him is driving.
Interestingly, while you'd expect Jetfire and Jetstorm to follow the trope (they even have red and blue color schemes, respectively), they avert the trope by both acting pretty red. Of course, they are working for Sentinel Prime, so who knows how that affects their personalities.
Sentinel Prime is the red who is reckless and an arrogant jerk, Optimus Prime is blue, being far more level-headed and humble to everyone. Ironically, Sentinel's primary color is blue, while Optimus' is red.
Then there's Bumblebee, who's Hot-Blooded, and Prowl, who is more mature and more experience in fighting.
In Transformers: Robots in Disguise, We have Sideswipe and Strongarm. Sideswipe, rebellious punk with a red paint job as the Red Oni and Strongarm, by the books rookie cop with a primarily blue paint job as the Blue Oni. In the 2001 series by the same name, there was serious, by-the-book Prowl who becomes a police car, and Side Burn, the cocky hotshot sportscar who keeps flirting with red sports cars (it's hard to know if he understands that they're not sentient... and harder to know what he thinks of his own Mid-Season Upgrade that makes him a red sports car).
Keith and Lance, as the Red and Blue Paladins respectively, embody this trope in battle. Keith is impulsive, hotblooded, and reckless, while Lance is strategic and level-headed. Ironically, outside of combat, they reverse this trope. Keith is stoic, reserved, and pragmatic, while Lance is passionate, emotive, and extroverted.
Wakfu has this dynamic between Amalia and Evangeline. Amalia is a Rebellious Princess who absconds for little reason other than boredom and brattiness. Meanwhile, Evangeline starts as a stoicTyke Bomb with Undying Loyalty to the Sadida royal family. She is all about duty and self denial and doing what's right. But as things go on, they both learn from each other and end up reaching more balanced positions on the matter of responsibility. Amalia learns from the example of Evangeline's courage and commitment, taking up the challenge of living up to her royal responsibilities and defending the Sadida kingdom at its darkest hour. Evangeline, at the same time, learns how to enjoy herself without compromising her duty.
Rogue and Jean, as the Red and Blue Oni respectively. Rogue is cynical, tough and more impulsive and willing to break the rules, while Jean is intelligent, nurturing and more levelheaded and willing to follow the rules.
In Xiaolin Showdown, examples on the villain side are Jack Spicer (red) and Chase Young (blue), while examples on the heroes side are Omi/Kimiko (red) and Raimundo/Clay (blue).
Yin Yang Yo! has Yang who is the aggressive red oni who like to go all melee, and Yin who is the calm blue oni who prefers to use magic. Their colors are inverted as Yang is blue, while Yin is pink.
In Young Justice the main team has Superboy, Kid Flash and Miss Martian as the Red to Aqualad, Robin and Artemis's Blue respectively. Red Arrow also plays Red to Aqualad's Blue when they're together.