Sableye, the Dark-type Pokémon from Hoenn, is found in the wild Pokémon Go. Yes, Sableye can be shiny Pokémon Go!
Unfortunately, despite his Mega Evolution, Sableye won't see much use in the game. It Is but a great shine. The change from the red rubies to the green emeralds gives a little “Finn from”. Adventure time finds out he is color blind.”
What is the shiny rate for Sableye in Pokémon Go?
According to old research from the now-defunct website The Silph Road (via Wayback machine), the shiny rate for Pokémon on a normal day is approximately one in 500. Sableye is not a confirmed Pokémon that receives a “permaboost” (meaning that it is a rare spawn and therefore receives an increased shiny rate).
What can I do to attract more shiny Pokémon?
Unfortunately not much. It seems to be a coincidence. Catch rates for Shiny Pokémon are set by developer Niantic and are typically only increased during special events such as Community Days or Safari Zones, or during Legendary Raids. There are no consumable items that increase the rate of Shiny Pokémon.