We're talking fire Pokémon turning into ice Pokémon and new colors for the oldie favorites. Introducing Alola forms, which will make their big debut in Pokémon Sun and Moon. Here are some of the classic Pokémon then depicted in their new forms, as courtesy of Serebii:
Pokémon Sun and Moon will also introduce the 'styles' feature -- which is dependent upon which parts of the island you encounter a given Pokémon on: