Can Yamask be shiny in Pokémon Go?
If you find a Yamask in the Pokémon Go wilds, does it have any chance to be shiny?
This article references relevant content from the polygon.com website. Original article link: [https://www.polygon.com/pokemon-go-guide/23889476/can-yamask-be-shiny-cofagrigus]

Yamask, the Spirit Pokémon from Unova, can be found in the wild in Pokémon Go. Yes, Yamask can be shiny in Pokémon Go!

Both versions of Yamask can be shiny. Whether you have a Galarian Yamask or the original Unovan Yamask, you can use the same candy to evolve and power up both.
What is the shiny rate for Yamask in Pokémon Go?
As per old research by the now-defunct website The Silph Road (via Wayback Machine), the shiny rate for Pokémon on a regular day is approximately one in 500. Yamask is not a confirmed Pokémon that gets a “permaboost” (meaning that it’s a rare spawn and thus gets a boosted shiny rate).
Not much, unfortunately. It appears to be random chance. Shiny Pokémon catch rates are set by developer Niantic, and they are typically only boosted during special events like Community Days or Safari Zones, or in Legendary Raids. There are no consumable items that boost shiny Pokémon rates.
LeekDuck keeps a list of currently available shiny Pokémon. It’s a helpful visual guide that illustrates what all of the existing shiny Pokémon look like.
For more tips, check out Polygon’s Pokémon Go guides.