What it does
Colbur Berry covers one kind of damage: when an opponent lands a super-effective Dark move on the holder, that hit gets halved and the berry is eaten.
Dark is worth covering because the meta is full of Dark moves built to remove Psychics and Ghosts. Knock Off hits the weakness and strips your item on the way through. Sucker Punch is priority — your Psychic doesn't even get to move before a Dark fist drops it. Colbur halves that hit, turning the priority punch from "KO" into "chip," and now you get to swing back.
That's the line between it and Focus Sash. Sash plus Sucker Punch has a trap: Sash needs full HP, and opponents often chip you with one move and Sucker Punch the next, which breaks the Sash first. Colbur works from any HP — it's built exactly for that chip-then-punch sequence. The cost is that it only covers Dark.
Who runs it
The carriers are almost all Psychics and Ghosts that fear getting picked off by a Dark move.
Oranguru (24%) and Farigiraf (22%) are slow, bulky support Psychics in doubles. Their biggest fear is a single Dark move taking them out before they do their job; Colbur buys the turn they need to set Trick Room or fire an instruction move.
Meowstic (15%), pure Psychic, takes Dark as a major weakness, and opponents keep a Dark attacker around specifically to remove it.
The Ghosts — Dragapult (11%), Ceruledge (13%), Sinistcha (10%), Chandelure (5%), Aegislash (4%) — are all Dark-weak, fast or fragile, and getting cleaned by a Sucker Punch is a common way they die. Colbur exists to break that line.
How to use it
The rule: save it for the moment you read a Dark move coming.
With your Psychic or Ghost on the field and a Dark priority attacker like Kingambit across from you, that's almost always a Sucker Punch. Eat the halved punch, stay up, keep the turn.
Sucker Punch has a quirk you can play around: it only works when you click an attacking move that turn — if you Protect or use a status move, it whiffs. So Colbur doesn't fire every game. Sometimes you guess right, Protect, and the Sucker Punch fails on its own without spending the berry.
Knock Off is different. It strips items, but a berry that's already triggered can't be knocked off. If that Knock Off is itself the super-effective Dark hit, Colbur halves the damage and is treated as spent — you've traded the halving for what would have been your item loss.
Tips & strategy
The most practical read is against a Dark-type like Kingambit. Its Sucker Punch is one of the hardest priority moves in the format to play around, so a Ghost or Psychic core with Colbur is insurance against getting punched out. After the halving you'll usually live to swing back, sometimes for the kill.
Don't give it to anything Dark doesn't hit super-effectively. Colbur only halves when Dark is super-effective; against neutral or resisted Dark it does almost nothing.
And it covers "this hit," not "this mon." After it triggers, the next Dark move lands at full power, so it saves a key turn, not the whole game. Check whether the halved hit actually keeps you alive first — if it still KOs, don't count on it.