In generation 6 games, most of the legendary Pokémon found in the main story are coded to never be shiny. Which of the Pokémon obtainable in Sun and Moon are similarly coded to never be shiny, whether they have to be caught or are simply given to the player?
According to Serebii this is the list of shiny-locked Pokemon in Sun/Moon:
- Tapu Koko
- Tapu Lele
- Tapu Bulu
- Tapu Fini
Probably also Magearna and Marshadow are shiny-locked like other Event-only Legendaries, they are listed in a different table.