Only static encounters can be shiny in RBY. Max. Optimizer is bound to know more about it than me, so you could ask them what you can and cant get.Hi again,
I found out something interesting and I wonder if it can be confirmed.
This video on the post states that wild pokémon in RBY can't be shiny because those DVs just don't appear on wild pokémon (but seems to be possible in gifts/starters/stationaries and.... fishing?).
So this would mean that like shiny Tauros with fissure/horn drill or any other Gen 1 exclusive move would be illegal. Afaik it can't be tutored in later generations either (unless move reminder can do that but I don't know).
This kinda sucks for me because I wanted to have a full rooster of shiny pokémon with exclusive moves from gen 1. :P