shinies didn't exist in generation one... however, due to the way that gen1 pokemon are coded, if you trade a pokemon from red, blue or yellow to a later generation, there is a chance that the pokemon has the necessary stats to 'become' shiny! there are a few ways of testing this. you can trade up the pokemon, examine its stats, or make use of a shiny indicator mod.
Accessed RANDOM FINDS (RBY)!