Koth, Fire of Resistance — ruling 1

Koth's emblem is colorless. Notably, this means that protection from red won't stop a permanent or player from being the target of the emblem's ability, nor will it prevent the damage being dealt. Replacement effects that care about damage from a red source don't apply to it.

Koth, Fire of Resistance : règles, fonctionnement et interactions (MTG)

Koth, Fire of Resistance is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

+2: Search your library for a basic Mountain card, reveal it, put it into your hand, then shuffle. −3: Koth deals damage to target creature equal to the number of Mountains you control. −7: You get an emblem with "Whenever a Mountain you control enters, this emblem deals 4 damage to any target."

How it works : Koth, Fire of Resistance

Original English text — Wizards of the Coast / Scryfall

#1February 4, 2023· Wizards of the Coast
Koth's emblem is colorless. Notably, this means that protection from red won't stop a permanent or player from being the target of the emblem's ability, nor will it prevent the damage being dealt. Replacement effects that care about damage from a red source don't apply to it.
No other card is named in this ruling.