About shinies list

Alolan Grimer is normally green. That's an Alolan one you hatched from a 7k egg. You can also tell it's Alolan because it's poison and dark type. Regular Grimer are poison only.

Lol it’s not a shiny it’s an Alolan grimer

Another dead giveaway is the lack of the shiny sparkles and the shiny symbol when viewed in storage. Shiny pokemon always have these visual effects that lets you tell apart confusing ones like EDIT: Plusle.

Thats an alolan grimer not a shiny grimer

The shiny variant is a slightly different shade of green, a bit more olive, as opposed to the blue-green of your Alolan Grimer.