Done to the point of overuse in highlights clips for the BBC's 2008 Olympic Games coverage.
The "Meet the Buttertons" ads for I Can't Believe It's Not Butter feature a typical 1950s family filmed in black and white, except for the bright yellow of the ridiculous amounts of butter they put in their food.
The commercials for Chase bank follow this trope, with the only color being the Chase logo.
TD Canada Trust, which are monochromatic except for the green of the bank's logo. The intention is invoke simpler times.
Both movie posters for Joss Whedon's adaptation of Much Ado About Nothing (which was filmed in black and white) use this. One has the movie's title in hot pink letters between the black-and-white faces of Beatrice and Benedick. The other shows Claudio mostly submerged in a pool, holding a cocktail glass in his hand; the cocktail is bright orange (with an orange slice) and the movie title appears in orange letters above Claudio's head. (In the movie itself, the cocktail appears in black-and-white like everything else.)
During a monochrome flashback showing Winry's parents death during the Ishval Civil War. All is in black and white except for the blue eyes of the amestrian soldiers and the blue eyes of Winry's parents.
Used in the first episode during the scene in which the Freezing Alchemist is killed.
The Deluxe Edition reprint of Batman: The Killing Joke has the flashbacks sequences in black and white with a different red object, progressively standing out more, to build up to the reveal of the Red Hood becoming The Joker.
Sin City: That Yellow Bastard had Junior (and his blood) constantly colored yellow after the prologue. Other stories, like "Blue Eyes" and "The Babe Wore Red" featured similar use of color. The movie added splashes of color to stories that didn't have them in print.
Wet Moon has no color in the actual stories, but the cover art depicts each individual character with a single thematic color, in their clothing and usually dyed hair.
Done in Soft Desire, which is a black and white comic with some color objects.
In the Captain America elseworlds miniseries The Chosen, the modern day middle east, including the soldiers stationed there and all of the locals are all depicted in shades of brown. This is meant to make Captain America stand out when he finally appears, as he is still wearing his primarily blue costume even in that setting.
Films — Animation
The emotional climax of The Prince of Egypt, where Moses meets with Ramses after his firstborn son is slain, was deliberately rendered in black and white with just a few hints of blue.
In the 1925 version of Ben Hur, all the scenes with Jesus are shot in color (even though he is not shown), as is Ben-Hur's triumph and the final scene.
Simiarly, in the 1927 Jesus movie The King Of Kings, the first scene shows Mary Magdalene lounging around with the Romans in color, and at the end of the film Jesus walks out of his tomb in color.
Early sound film Hell's Angels has the fancy dress ball scene in color. This is the only color footage of Jean Harlow's career.
The pre-titles sequence of Casino Royale. The first splash of color in the film is the blood from the Bond Gun Barrel (which is moved to the end of that sequence and integrated into the plot — it's the POV from the gun of one of Bond's targets).
In Schindlers List, Spielberg uses red to highlight a single Jewish girl's coat — once as she's being taken to a ghetto, and again as her body is being taken to a mass grave. The candle flames are also in color when the Jews celebrate the Sabbath for the first time since being hauled out of the ghettos and into concentration camps.
Spielberg may have lifted this visual idea from Dutch film Het meisje met het rode haar, The Girl With The Red Hair (1981). The only thing in colour in the movie is Resistance heroine Hannie Schaft's red hair - everything else about grim wartime Holland is in grey.
Samurai Fiction, a spoof of traditional samurai epics striving towards art-film stylism, is black and white except for splashes of color used for dramatic effect.
The 1987 Wim Wenders film Wings of Desire has most scenes filmed in black and white or sepia, except for a few scenes featuring only the female lead, which are supposedly not from the point of view of the angels.
The Spirit is in black and white (though some scenes are so gray they might just be desaturated) except for the Spirit's signature red tie and a handful of other things like yellow police tape and a few closeups with red lipstick.
Alfred Hitchcock's Spellbound is filmed entirely in black and white, except for a couple of frames of red inserted at the climax when the villain commits suicide.
In Pleasantville, a brother and sister travel back to a 1950s town, which is originally in black and white. Their influence leads people to develop color as they learn to think for themselves.
Person-specific example: In The Muppet Christmas Carol Scrooge dresses entirely in monotone. When he goes out at the end of the film he puts on a red scarf given to him by Beaker, showing his changed personality.
In an episode of Monk, Stottlemeyer's case-solving (which is normally black and white) is showing purple napkins, which were at both places.
In the short-lived series John Doe, the protagonist is colorblind, so the things shown from his point of view are shown in black and white. However, in the pilot, when he sees the news about a missing girl, her face shows color and Doe is convinced the girl is related to him somehow. She wasn't, but every other time the "warning colors" appeared during the series, they were things related to him (like the woman in the green scarf, or the Phoenix statue).
VR5 played all sorts of games with color during the VR sequences. Typically, unimportant objects were desaturated, while important ones were supersaturated.
Used extensively in the TV version of Half Moon Investigations for scenes showing how the Crime Of The Week was actually commited (black-and-white otherwise), most notably with spot colour on the pink clothes worn by the Pinks and a yellow jacket that was a Clue. Never two different colours in the same scene, though.
Season 2 of Breaking Bad featured several Cold Opens which foreshadowed an accident scene, with hazmat-besuited men sifting through debris. The only thing in colour was a pink teddy bear (with an unsettling likeness to Lotso...)
Cold Case episode Forever Blue does this. All of the flashbacks to the time the murder took place are set in black and white outside of the red colour on the police car and the white/yellow glow from certain lighting (candles in the church and a lamp)
In Once Upon a Time, Dr. Frankenstein's world is in black and white, but the visiting Rumplestiltskin (and the gold he gives Frankenstein) are in color.
Inverted in the Velma Mulholland sketches on In Living Color!. Velma is a 1940's film noir-type character and was always shown in black and white, while everything else is in color. Even her apartment and her car are in black and white.
Italian singer/songwriter Gala's video for Faraway has this.
Queen's video for "I'm Going Slightly Mad" is nearly all B+W, but there is a feathery cape that Freddie Mercury flings near the end that is in vivid rainbow colors.
The video for "The Perfect Drug" by Nine Inch Nails shows everything in blue-tinted monochrome, except for one green drink of absinthe. The ensuing trip switches to a green tint.
The video for "Blame It" by Jamie Foxx shows everything in red-tinted monochrome, except for white camera flashes and blue drink glasses.
The video for Of Monsters And Men 's "Little Talks" is all in black and white except for the girl made of sunshine and rainbows, who is in every colour. At the end, so are the beings from her domain.
The video for Elton John 's "Sad Songs Say So Much" has everything in black & white except Elton himself and a few neon signs.
In Frazz, a colored egg is the splash in a monochromatic Sunday strip.
In The Saboteur, the eponymous protagonist sets about World War II Paris giving the people the will to fight back. Upon restoring a given district's willpower, it will go from black-and-white to dazzling color. Until this happens, however, the only color at all is the bright red on Nazi symbols and the occasional bit of blue on your allies.
In Wizball, you played a wizard boarding a green bouncing/flying orb with a face in order to bring color back to the various worlds. At first, the worlds were in drab monochrome, but once you directed your cat's own orb to catch enough paint you returned to the lab, after which one of the three colors of that particular world was restored.
In The Legend of Zelda: The Wind Waker, when you first visit Hyrule castle after it's frozen in time, it's completely in black and white. Notable because it's a very sharp contrast to the bright, cel-shaded graphics in the rest of the game, and to Link himself as he is still in color as he runs around.
Shadow Of Destiny revolves around the use of time travel to change your fate— each era you travel to has a different color tone. The modern day is in bright, normal colors, slightly older is a bit off, the turn of the century is black and white, and the 16th century is sepia tone. Oddly enough, your character doesn't change color when he travels, and stands out against the background.
The 11th Hour normally plays in color, but has an option to play instead in black and white, with only the puzzles and cutscenes in color. For an added touch, this mode also adds an artificial film grain.
Katamari Forever casts several stages in monochrome, gradually adding color to show which items you're able to collect as your katamari grows bigger.
In Brütal Legend, when the Skies Afire spell is active, the color pallette switches from full-color to black, white, and orange.
Mario/Luigi in World 6-3 in Super Mario Bros.. The SNES remake, on the other hand, had this level colored normally, which in turn defeats this purpose.
The cutscenes in Prototype 2 are entirely black and white, except for virus powers and the lights on Blackwatch technology, which glow red and blue respectively.
In Mutant Mudds, traveling through the secret V-Land and G-Land gates turns the backgrounds Deliberately Monochrome (grey for G-Land, and blood-red for V-Land), while leaving the color palettes of Max and the Mudds untouched.
When Annie uses the blinker stone to see into the Ether, any non-magical people and objects are shown in black and white. So, when looking through Ether-vision, the Court becomes grey with some splashes of color, while Gillitie Wood becomes far more colorful.
Renard/Reynardine's original body is also in greyscale, since it's waiting for his soul to come back from Annie's plushie. See here.
Lackadaisy is colored in the sepia tones of faded 1920s photographs. The only color that ever shows up is red - be it blood, flames, or the flowers that sometimes show up on people's suits.
Fans! had this recently when they needed to point out for plot reasons that two characters (one a parody and therefore inferrable, but the other entirely original) had the same hair color. This came after over ten years of nobody caring.
Ow, my sanity has the Delta Green symbol and some magic effects, while everything else is black pencil.
The first part of Juathuur is in black and white, save for the occasional color page and Mijuu's blood in chapter 22.
Archipelago has only magic spells-including telepathic communication-and the cover pages colored.
Terminal Lance is drawn in black-and-white, with the exceptions of reflective belts, which appear a bright vivid yellow.
Wapsi Square is almost exclusively in black and white. However, color is used in Shelly's "boiler room" mental landscape. Unearthly color, but color none-the-less. This is probably to represent the alien, existing on multiple levels of reality nature of the place.
The Roommates and also its Spin-OffGirls Next Door are black and white... except for covers and specials. If you see color in the regular pages it's probably there for a reason like in the panel of James' speech about second chances got a fully colored sunrise.
The flashback sequence of Remus is drawn in greyscale with spots of color for certain eyes, blood, and gunfire.
The comic Namesake uses this. Because the artist does not have time to make the comic fully in color, she limits colors to significant scenes/elements. Ex: Red for the poppies in Oz. To some this is actually part of the appeal of the comic
The season 1 finale of Avatar: The Last Airbender uses a very dramatic version when Zhao killed the moon. First red light spreads like a bloodstain once the moon spirit/koi is captured and then the entire city loses all color when Zhao kills the moon spirit. Only firebending attacks and Princess Yue's blue eyes are shown in color.
An episode of The Fairly OddParents in which Timmy wishes everything is the same turns everything gray and blobby, leading to Cosmo and Wanda being unable to find Timmy. However, since before the grayification, Timmy's mom tried to make a pink souffle and it collapsed and turned gray, blob-Mom's souffle collapses and turns pink, allowing Timmy to make his signature pink hat and unwish the wish.
In another episode Wanda disappears and Timmy wishes everything was like a black-and-white noir film, but Cosmo missed a corner of one room.
Animaniacs has a fair share of B&W segments, in all of which the Warners still retain their red noses.
Including one literal use of this trope: a documentary style interview with an old star about the Warners back in the day has her mention that the Warners would go around "painting the town red, literally". Cut to a shot of them splashing red paint all over a black and white city.
The Disney short Paperman (released with the feature Wreck-It Ralph) is in B&W, except for the pretty girl's lipstick (and the imprint it leaves on a paper), which is in red.