No, you cannot catch the shiny version of Popplio in Pokemon GO.
As Popplio only came to Pokemon GO in March last year, game developer Niantic has not added the shiny version of it just yet. It usually takes at least a year for shiny versions of new Pokemon to debut.
However, you may want to farm some Popplio Candy for when shiny Popplio arrives in the games. If so, don’t miss the Pokemon GO Popplio Spotlight Hour!
Or, if you’re a shiny hunter, you’ll want to know the exact odds of encountering shiny Pokemon in Pokemon GO!
When Will Shiny Popplio Come to Pokemon GO?
Pokemon GO developer Niantic has not confirmed when the shiny version of Popplio will come to Pokemon GO yet.
Shiny Popplio will likely come to Pokemon GO in Summer 2023. By this point, it will have been over a year since Popplio was released in Pokemon GO.
Find out whether you can catch shiny versions of the other Gen 7 starters in Pokemon GO:

What Does Shiny Popplio Look Like?
Shiny Popplio is navy blue with a light pink collar around its neck. This makes it appear quite different to the standard blue Popplio with a light blue collar.
Shiny Popplio’s eyes, face, and nose are the same as the normal version.

Can You Get Shiny Brionne and Primarina in Pokemon GO?
No, you cannot get shiny Brionne or shiny Primarina in Pokemon GO yet. This is because shiny Popplio is not currently in the game.
Once shiny Popplio comes to Pokemon GO, you will be able to evolve it into the shiny versions of Brionne and Primarina.
So you’ve got enough Popplio Candy to evolve a shiny Popplio as soon as you get one, make sure to find out how to boost the amount of Candy you earn!