Next to depicting loss of bowel or bladder control, there's few things more inherently gross than showing someone throwing up. It's an instinctually revolting sight, and everything about it can easily cause people nearby to lose their own lunches, or at least feel like they might. So how do you have characters upchucking without potentially squicking out the audience? Simple—show the character with a rainbow-colored stream of liquid or light coming out of their mouth.
This usually shows up in three distinct contexts. In one, it serves as an eye-catching way to get across what's happening while downplaying its nastiness. Other characters may react as expected when seeing the character yark, but the audience will likely have few or no ill effects from the scene. Rainbow vomit used in this way is very prominent in anime, mainly because it's an Enforced Trope in Japan due to certain censorship rules for television.
Another is in works that prominently feature non-human characters, especially those which wouldn't be expected to have a digestive system, aren't technically living creatures, or or are magical or alien to some degree. Having such a character have rainbow-colored vomit, along with being less gross than regular vomit, is an effective way to lampshade their not being human.
The third is considered to be a Reaction Shot towards objects or creatures that are Sickeningly Sweet or can induce Cuteness Overload.
Sister Trope to Black Blood and Blue Liquid Absorbent, where blood is recolored to something less squicky in TV shows and advertisements respectively, and Vomit Indiscretion Shot, which is usually the more icky version and shows up in darker or more serious works. Stress Vomit and Waterfall Puke may also be depicted in this fashion.
Contrast Bad Black Barf.
Examples:
- Chainsaw Man: The (in)famous scene where Himeno pukes in Denji's mouth when they're kissing is pixellated in the anime proper. However, the ending "Chu, Tayousei" has a repeat of the scene but with rainbow vomit instead.
- Is This A Zombie?: In one episode of the anime, Ayumu catches Chris drinking in a room by herself. She's initially shocked, then seems to calm down, only to get sick and throw up a rainbow stream with glowing flowers in it. She then falls off the stool she was sitting on, laying beside the rainbow puddle and cradling a bottle of booze.
- KonoSuba: The pub party montage in the first episode of the anime adaptation ends with Aqua throwing up outside the pub as Kazuma watches, depicted as a rainbow waterfall with various glowing things inside. The opening for season 2 continues this trend, and in The Movie her fellow goddess Eris is also shown to vomit this way.
- My Hero Academia: If Ochako overuses her Quirk, Zero Gravity, she becomes nauseous and throws up. This is always depicted in Vomit Discretion Shots, with a sparkly glow around her head that cycles through rainbow colors.
- Naruto: During the Mecha-Naruto filler arc, the eponymous villain targets Naruto and Yamato while they are being carried on a palanquin. The ensuing chase triggers Yamato's motion sickness, whose nausea is comically represented by a shot of him flying through outer space while a colorful stream flows through his mouth.
- Overlord: In "A Handful of Hope", when Ainz confronts the members of Foresight, Arche says that he is lying about his magical abilities. He then removes the ring that was concealing them, and when Arche scans him, she's so horrified at learning the true extent of his power that she falls to her hands and knees, pukes out sparkling vomit, and begins babbling.
- Pokémon the Series: Sun & Moon: In "A Shocking Grocery Run!", Ash tries cooking his own food while Kukui is out. The result causes him to puke rainbow sparkles all over Pikachu, making him shock the entire house. This was edited out of the English dub and we only hear the puking noises.
- Scarlet Lady: When Tikki is forced to use the Miraculous Cure by herself (due to Chloé being unavailable), she eats the black akumatizing butterfly before vomiting up a literal World-Healing Wave of magical ladybugs — so many that the entire Le Grand Paris hotel is flooded.
- Played for Drama in Twinkling in the Dark; due to the excess happy energy poisoning his body, Joker at one points vomits a rainbow.
- Chip 'n Dale: Rescue Rangers (2022): In the prologue, showing Dale's first day at school, he tries to impress his new classmates by pretending to jab a pencil into his eye. The students are frightened and grossed out by this, with one of them, a cartoon unicorn, vomiting a rainbow into her lunch bag.
- The LEGO Movie 2: The Second Part: One of the Stars vomits a stream of rainbow glitter after being spun around and used as a weapon by General Mayhem.
- In Pleasant Goat and Big Big Wolf: Dunk for Future, Paddi overexerts himself playing a game of basketball. When Slowy gets mad at him, he pukes a rainbow.
- Green Day: The censored cover art of Father of All Motherfuckers partially blocks out the "motherfuckers" in the title with an anthropomorphic unicorn vomiting a rainbow. In the album's uncensored cover, the unicorn is absent.
- Angels of Death: When Rachel asks Zack to kill her, he vomits in rainbow colors, absolutely disgusted with the idea of killing someone who wants to be killed.
- Family Flights: Whenever your plane experiences turbulence, some of the passengers may get sick and throw up rainbow-colored streams which the player has to clean up as a task.
- Honkai Impact 3rd: In the "Valkyrie's Cafeteria" event, one story scene features Rozaliya and Liliya making some dishes so they can livestream themselves eating them as a promotional piece. However, when Rozaliya eats the dish Liliya made, she reacts with disgust and then starts uncontrollably throwing up. When this starts, she's shown with a rainbow stream shooting out of her mouth.
- Honkai: Star Rail: In the Golden Hour level in Penacony, SoulGlad is the official drink of the world and some parts of the level are literally fueled by it. Several NPCs can be seen wandering around and vomiting neon rainbows because they've clearly had a bit too much to drink. One NPC in particular, Dancy, can sell the player Aideen Park tokens when he's not in the middle of puking neon rainbows.
- Master Detective Archives: Rain Code: Shinigami pukes out the solution keys in rainbow colors before starting a labyrinth. When it's pointed out, she asks if they should come out of "some other hole then", and later she confesses that she could have just handed them over normally, but hadn't since Yuma didn't ask her to.
- Moshi Monsters: At the end of the song "The I.G.G.Y. Chomp", I.G.G.Y., who's been eating all kinds of things non-stop throughout the song, gets sick and throws up rainbow-coloured fluid onto the screen.
- NEEDY STREAMER OVERLOAD: In a rare dark take, the "Internet Overdose" ending shows Ame-chan/KAngel puking rainbow-colored Stress Vomit during a livestream in response to the stress she has been undergoing from her streaming work and from mean comments. Unfortunately, people start calling her "Puke Girl" in the stream comments and never let her live it down, which just compounds her stress and eventually leads to Sanity Slippage.
- ASDF Movie: One segment has a guy seeing a doctor to tell him he thinks that he is a homosexual. When the doctor asks how he can tell, the guy starts puking a rainbow.
- Battle for Dream Island: Puffball and Puffball Speaker Box can vomit a noodle-like rainbow-colored substance, both voluntarily and involuntarily; the latter is usually due to stress or injury. This is seen in in "Zeeky Boogy Doog", Get in the Van", and "BFB Back from Beginning".
- Charlie the Unicorn: In the first episode of the parody spinoff "charlie teh unicron", Pink randomly throws up a rainbow while he and Blue are talking to Charlie...in the middle of a forest fire.
- Disney: In "Finding Dory as Told by Emoji", the ending has Gerald coughing up a rainbow for no reason.
- hololive: Subaru, Okayu, and Mio played a game of Mario Party, with the loser having to eat a ball of wasabi as punishment. That ended up being Mio, and she promptly threw up. One clip of this appropriately gave her a stream of rainbow puke in the video's thumbnail.
- hololive - Holo no Graffiti: "This Is Dope!" starts off with Koyori accidentally freezing herself. After Mio and Miko thaw her out, she throws up a stream of rainbow-colored capsules.
- Mappy: In Episode 5, the Prince from Katamari Damacy gets sick, and ends up throwing up a rainbow at one point.
- The Colors of Evil: The end result of somebody who suffers Cuteness Overload from Belphagor's demon is them blasting a rainbow from their mouth before collapsing.
- Red Minus: The Nyan Caxx video shows Caxx, after watching days of non-stop Nyan Cat imagery, snapping and seeing a barrage of increasingly nightmarish imagery, which leads to her violently vomiting a rainbow stream into a toilet just before the credits roll.
- Bailin and Li Yun: In Strip #24, as Li Yun is taking Bailin to his apartment, Bailin gets carsick and throws up a digitally mosaic-ed rainbow stream in the backseat.
- Cursed Princess Club: Princess Maria, who is a fear vomiter, ends up puking a sparkly rainbow when Blaine and Lance bring the Pastel Princesses to a "Disgusting Bloody Clown Murderhouse" at the amusement park. In the aftermath, Blaine tells Maria that "somehow even your vomit is beautiful... As well as quite patriotic...!"
- Fire Emblem Heroes: A Day in the Life: Draug pukes up rainbows after moving too much through his allies' support.
- Anime America: Robyn occasionally shows fangasming in her videos by making her animated avatar vomit a rainbow.
- Corridor Digital: "Potion Overdose" shows that puking rainbows is easily the mildest side-effect of, well, a potion overdose.
- The Puking Rainbows meme. It started as a commentary about the labeling of Japanese snacks, and became an art contest about rainbows throwing up rainbows, and escalated from there. It has since been appropriated in Rage Comics towards gush-worthy things found on the Internet, as this commenter says it:
Commenter: There's an alternate meaning/usage for Puke Rainbows, it's used as a reaction shot when something tastes like diabetes. Yes, TV Tropes has ruined my vocabulary.
- TomSka: In "Imaginary Friend", Mr. Tibbles pukes a rainbow in shock upon Lily revealing she built a bomb as a present for him. Later, when Mr. Tibbles' parents barge into Lily's room and see him holding the bomb, his father also pukes a rainbow in shock.
- Smosh: In "Parents SUCK!", Anthony defiantly binges on Skittles, then is showing throwing up a rainbow stream of the candies.
All these whack fruit snacks with only five in a pack...
"Only eat one!" F*ck that, I'll snack till I yack!
- Adventure Time: In "The Monster", Lumpy Space Princess vomits a rainbow after eating tree bark.
- The Amazing World of Gumball:
- In "The Apology", the class is horrified by Miss Simian's exposed rear and everyone reacts in various ways. Masami, a floating cloud, vomits a rainbow. Amusingly, the side effects of what she's talking about mention "nausea" right as this happens.
- In "The Joy", Gumball and Darwin are infected with the Joy Virus. The last symptom they exhibit before succumbing to the disease is vomiting a star with a rainbow trail. They then reanimate as "happy zombies", who constantly drool a rainbow-coloured fluid.
- DuckTales (2017): Dewey introduces Webby to a game called Yuke or Puke which has a character that pukes rainbows when you do well at the game and subverts this trope when you do poorly.
- The Epic Tales of Captain Underpants: In "The Bizarre Bout of the Beastly Barfilisk", looking the Barfilisk in the eyes elicits this response from various campers.
- Gravity Falls: One of the oddities about the gnomes living in the forest outside Gravity Falls is that for some reason, they puke rainbows that sparkle as they splash on the ground.
- Middlemost Post: In "Challenges", one of the challenges between Angus and Parker is to guzzle down milk. Parker manages to defeat Angus, but immediately throws up a rainbow which hits both Angus and Russell.
- Moon Girl and Devil Dinosaur: In "Coney Island Baby", Casey mentions early on that she likes to eat colorful food before getting on rides, so that when she pukes it comes out as Rainbow Puke. At the end, both Lunella and Casey throw up after a ride and go "oooh" at the colorful puke.
- Total Drama: In "The Wheel of Vomit", Chris has the breakfast gruel dyed different colors, knowing very well it would be seen again. Later, after Julia wins immunity, Chef tries announcing it, only to vomit out a rainbow. This causes everyone else to vomit rainbows as well, including the camera crew.