The two most popular footballers, Cristiano Ronaldo and Lionel Messi. The prideful Ronaldo is the red oni to the humble Messi’s blue oni. Appropriately, Ronaldo’s national team (Portugal) kit is red, while Messi’s (Argentina) is sky blue.
Vince Lombardi and Tom Landry (Red and blue respectively) coached one of the greatest games in American Football history against each other, the 1967 Championship game. Lombardi was described as a very passionate, hot-blooded coach who would celebrate every success and and mourn every setback with equal gusto, whereas Landry was very calm and stoic. Ultimately, Lombardi's Packers beat Landry's Cowboys 21-17. They also played the same red/blue roles when together as assistants for the NY Giants - Lombardi coaching the offense and Landry coaching the defense.
Shaquille O'Neal (red) and Tim Duncan (blue)
Karl Malone was the blue (blue-collar work-ethic, more reserved demeanor) to Charles Barkley's red oni (party animal, loud, very outspoken). Among the Utah Jazz, though, Malone was red (earthy Southerner) and John Stockton (serious Pacific Northwesterner) was blue.
Martina Navratilova and Chris Evert had a long-running Friendly Rivalry in the 1980s with Navratilova being the more openly emotional and passionate one and Evert gaining the nickname of "Ice Queen" for her cool and steely demeanor on court.
The choleric John McEnroe and the imperturbable Björn Borg had one of the most famous tennis rivalries in spite of its relatively short length, mainly because of their perfectly contrasting "fire and ice" personalities. Additionally, the robotic-seeming Ivan Lendl could be said to be a replacement blue oni for McEnroe after Borg's retirement.
Venus Williams (blue oni) and Serena Williams (red oni).
The giggly, bubbly Monica Seles was the best-known and most successful rival to the cool-headed, stern-lipped Steffi Graf.
USC and UCLA. The Trojans in cardinal and gold tend to be more proud and arrogant as the red onis, while the Bruins in True Blue and gold tend to be more intellectual and nerdy.
City rivals Rice (blue) and Houston (red) fit this trope to a T, in both their student body profiles AND their respective choices of school colors.
As do Kentucky (blue) and Louisville (red), though more in general social dynamic than in student body profiles (especially in the 21st century).
The University of Georgia and Georgia Tech. The colors even match, as Bulldogs (in red and black) are rough and rowdy sports fans while the Yellow Jackets (in white, gold, and navy) had a reputation for being intellectual "engine-nerds."
Boston Red Sox (blue collar, ironically) and New York Yankees (metropolitan). Like Dr. Manhattan, everyone is a hot-blooded underdog compared to the New York Yankees.
Anaheim Angels and Los Angeles Dodgers (just for color, they both used to be blue)
The Washington Capitals and Pittsburgh Penguins, embodied by the playing styles and personalities of their respective superstars: the Caps' Alex Ovechkin (red) and the Pens' Sidney Crosby (blue). Appropriately, Washington's primary color IS red, while Pittsburgh used blue as its primary color until 1980 and recently brought it back for their alternate jersey.
Eternally present in European Football Clubs, especially as most local rivals tend to wear Red and Blue to contrast each other intentionally.
In Italy's Serie A, AC Milan wears red, and they're a passionate club, with a fanbase mostly from the lower class. Inter wears blue and their policy is calculating, with their devoted fans coming from the upper class.
Manchester United and Manchester City. United is the much more fiery one, given their huge fanbase (accounting to 5% of the world's population) and the number of silverware they accumulated over the years. City is much more closer to the upper class Mancunians and residents of the city proper, in contrast to United's wider demographic.
Arsenal and Tottenham Hotspur, also known as the North London Derby. Arsenal is Red, with a very diverse multiethnic fanbase. Tottenham is Blue and is supported by the conservative Jewish population of London.
A teammate example: Italy's and AC Milan's midfield duo, the fiery, aggressive Gennaro Gattuso and the cool, efficient Andrea Pirlo.
The Paris St. Germain strike pairing of the arrogant, explosive Zlatan Ibrahimović and the calm, methodical Edinson Cavani.
Another teammate example: Chicago Blackhawks stars Jonathan Toews and Patrick Kane. Together the two are the face of the team and, to an extent, the NHL as a whole. Kane tends to be a bit more excitable both on and off the ice while Toews exhibits a much more cool and collected personality.
In English football:
Luis Suárez, the fiery Uruguayan with a penchant for spectacular goals and a knack for being controversial, is the red oni to the blue oni of Sergio Agüero, the methodical Argentine who's a cold-blooded, clutch finisher with sound fundamentals. This becomes even better when you look at the jerseys of their clubs. (Luis Suárez - Liverpool, then Barcelona, Sergio Agüero - Manchester City)
Mesut Özil and Alexis Sanchez during their days at Arsenal. Özil is the cooler, less expressive and less flashy player, who prefers passes and assists. His cooler side leads to him being accused of not caring, just because he tends to show no real emotion or frustration when compared to the rest of his team, despite him putting in one of the highest work rates of anyone. Alexis Sanchez, on the other hand, is the flashy, expressive, emotive winger who is not afraid to let his feelings be made known, and has caused major transfer drama as a result, eventually culminating in a move to rivals Manchester United.
The three major Texas public colleges fit a slightly mutated version of this trope. The University of Texas is the high profile, upper class, some would say snobbish blue oni. Texas Tech is the hot blooded, unsophisticated, very red scrappy. And Texas A&M is kind of the purple middle man, who can fill either role depending on which of the other two they're facing next...
NFL team the Pittsburgh Steelers have a pair of outside linebackers who sort of fit. LaMarr Woodley is the Red Oni and James Harrison is the Blue Oni. LaMarr is more talkative, more likely to celebrate (every sack he records is followed by the most awkward flying side kick ever witnessed), and generally more energetic. James is a quiet, not-quite-right-in-the-head fellow with a penchant for perpetrating unspeakable violence with little noticeable emotion.
The two NFL teams in the NYC area: The Giants tend to be the Blue Oni (reserved, hard-working players in a clear-cut meritocracy where production on the field is all that matters) to the Jets' Red Oni (even though the Jets actually wear green, and the Giants have more red in their color scheme than the Jets do), who tend to have a lot of bluster. This came to a head in 2011 when both teams faced each other on Christmas Eve: the Jets talked a lot of trash before the game, even covering up the Giants' mural of previous Super Bowl championships (both teams share the stadium, but as the designated "home" team, the Jets had control over the stadium itself). The Giants didn't respond much to this... at least in the media. On the other hand, they completely destroyed the Jets, ending their playoff hopes and starting the Giants on a journey to their fourth Super Bowl title.
The two faces of the New England Patriots, Tom Brady is the red and Bill Belichick is the blue. Tom Brady is a fiery leader and oftentimes serves as The Heart of the team, even being one of the main motivators in the late stages of the game when they are down. He is also very expressive, routinely high-fiving other players (when they actually return them◊) and even outright jumping for joy when Malcom Butler made his game-winning interception against the Seahawks in Super Bowl XLIX◊, and that's not even counting his social media activity. Bill Belichick, however, is... not. His unflappable exterior has reached memetic levels, he refuses to play the social media game his quarterback does, is often seen as a “Stop Having Fun” Guy due to his incredible focus on winning (he once banished a player to the Cleveland Browns for asking for more money, after which the Patriots went on to win the Super Bowl), and even once spent the Super Bowl Parade trying to start a "No Days Off!" chant.
The Seattle Seahawks are known for 2 players. On one hand you have the brash, outspoken, hype-machine that is cornerback Richard Sherman. On the other hand you have the calm, cool and collected quarterback known as Russell Wilson.
The Calgary Flames and Edmonton Oilers of the late '80s were an inversion. The blue-coloured Oilers were young and high-scoring, led by the likes of Wayne Gretzky, Mark Messier, and Jari Kurri, while the red-coloured Flames played more of a defensive, tight-checking game.
The University of Arizona and Arizona State University are both red-ish in both school colors (Arizona's is cardinal red and ASU's is maroon) and reputation (both are party schools) but Arizona is considered to be a better academic institution and also has navy blue as its other school color, while ASU's second is gold.
Sports/sports culture in general: American football is red to baseball's blue.
Hunting is red to fishing's blue.
American Football is red to association football (AKA Soccer)'s blue (its fandom notwithstanding). Australian football is somewhere in the infra-red spectrum.
The very jovial, talkative, and friendly Hélio Castroneves is the red oni to the much more calm, stoic, and businesslike blue oni of Scott Dixon, who beat him out for the 2013 championship. Ironically, Castroneves' normal livery is a black and white one (with the occasional red and yellow or blue and white livery depending on the event), whereas Dixon always drives a red car.
Alex Zanardi ('96-'98) and Juan Pablo Montoya ('99-'00) and Jimmy Vasser made an excellent case of Red Oni/Blue Oni teammates en route to winning four CART titles in five years.
Brazil had in their women's basketball Hortência (Red) and Paula (Blue), who had sort of a rivalry (they noted that every tournament ended with a final between their teams) but then turned into a Friendly Rivalry in the national team, that even beat the US Team in the 1994 World Championship - two years before losing to them in the Olympic Games final, but the silver medal was the first for Brazilian basketball in over 30 years!
University of Utah (crimson and white) and Brigham Young University (blue and white) fit their colors well. BYU, as a church-operated school, comes across as serious and a bit aloof. Utah has taken on the role of the boisterous counterpart by default, but some fans really get into it. A lot of it is affected, though, since BYU and Utah are very similar academically (though because of enrollment caps BYU is harder to get into).
School colors also hold true for University of Nevada, Reno (blue and silver) and University of Nevada, Las Vegas (scarlet and gray). UNR is older, more academically respected and started branding their sports as "Nevada" after UNLV became prominent, hoping to distance themselves from their rival and emphasize that they're older. UNLV is larger and has had frequent run-ins with the NCAA, especially in its most prominent sport of men's basketball. And it extends to the cities as well: Vegas as a flashy party town, Reno as more sedate and humble.
Some college archrivals have the proper contrasting colors but generally avert this. Harvard (crimson) and Yale (blue) are both very elite and exclusive, with Harvard probably having a very slightly higher reputation. UC Berkeley (blue and gold) and Stanford (cardinal and white) have similar reputations, with Stanford, as a private school, being a touch more elite. But the notorious antics of the Stanford Marching Band are firmly in Red Oni territory.
In New Zealand rugby, the Auckland Blues (team colour: blue and white) and the Canterbury Crusaders (team colour: red and black) invert this trope. The Blues play with attacking flair but are prone to errors, whereas the Crusaders are traditionally known for their structured plays.
Even though they both use green as their main school color, North Dakota State University (Red Oni) and University of North Dakota (Blue Oni).
From the 80's Chess, Anatoly "It"s important for players to avoid displaying emotions" Karpov versus Garry "I am emotional and ready to take risks" Kasparov.
In German football, the passionate, attacking Borussia Dortmund (red, although they wear yellow) to the relatively calmer Schalke 04 (blue.)
In the Philippine Basketball Association, Barangay Ginebra (red) and Star (blue), especially when their rivalry was just heating up in the late '80s-early '90s. Ginebra, with matching red uniforms, was known as a blue-collar team in the fashion of the Detroit Pistons "Bad Boys" of the same era, and has been known as the "team of the masses" since the mid-'80s. Star, then called Purefoods and wearing matching blue uniforms, was a team of young, good-looking, yet talented "glamour boys" and generally appealed to more upscale PBA fans.
In golf, Arnold Palmer and later Lee Trevino (both red) to Jack Nicklaus (blue).
This is fairly evident in a number of rivalries in mixed martial arts (MMA), and especially the UFC. Often one of the fighters will be more aggressive, more of a trash-talker, and more of an upstart, compared to the other's quieter, more collected, more technical approach:
Jon Jones (red) vs. Daniel Cormier (blue)
Conor Mc Gregor (red) vs. Nate Diaz (blue), though in most other rivalries it is the Diaz brother who is the red, e.g. Nick Diaz (red) vs. Georges St. Pierre (blue)
Chael Sonnen is the red to his opponent's blue.
Michael Bisping (red) vs. Georges St. Pierre (blue)
Tyron Woodley (red) vs. Stephen Thompson (blue)
Dominick Cruz (red) vs. Team Alpha Male (blue). Fittingly, whenever a Team Alpha Male fighter would fight Cruz, they would fight in blue shorts. Though this began to reverse during the actual fight of Garbrandt-Cruz.