Dratini has always been available in its shiny variant in the game, but for its Community Day event, it’ll be found more frequently in the wild. While Dratini is usually blue, the shiny variant is pink instead.

Shiny Dragonair, the next evolution, is also pink, while its final evolution, Dragonite, is green instead of it traditional orange color.

Source: https://www.distractify.com/p/can-dratini-be-shiny-pokemon-go