Do shinies evolve into shinies?
SneakyGremlins Of course! It would be a bit shit if they didn’t 
However, a shiny Pokemon’s first form colour isn’t always the same as the second or third form colours.
For example, shiny Charmander is a pale yellow, but shiny Charizard is black.
Similarly, shiny Magikarp is yellow/gold, but shiny Gyarados is red.
Shiny Dratini and shiny Dragonair are pink, but shiny Dragonite is green.
But of course you do get Shiny Pokémon where the colour is the same in both or all evolutions eg. shiny Wailmer and Wailord are both purple, shiny Mareep, Flaaffy and Ampharos are all pink, shiny Swablu and Altaria are both yellow/gold etc.
Whatever it’s evolution colour changes, all shiny forms stay shiny once evolved 