A Pokémon of a Different Color! - S16.E39

On Cave Island, Ash and his friends meet up with Clair, Gym Leader of Johto's Blackthorn City, who has come to the island to capture a different-colored Druddigon, but her Dragonite left without her. When they find her Dragonite, Iris's Dragonite takes an instant dislike to it and the two fight, hampering Clair's plans to find the different-colored Druddigon on the other side of the island from the port.