This is a List showing which Pokémon arent in which game. This list is quite handy if you cant find a Pokémon
Red(These Arent in RED)
These Are Sandshrew, Sandslash, Vulpix, Ninetales, Meowth, Persian, Bellsprout, Weepinbell, Victreebel, Magmar, Pinsir and Mew
Blue
(These Arent in Blue)
They are: Ekans, Arbok, Mankey, Primeape, Growlithe, Arcanine, Oddish, Gloom, Vileplume, Scyther, Electabuzz and Mew
Yellow
(These arent in Yellow)
These Are Weedle, Kakuna, Beedrill, Ekans, Arbok, Meowth, Persian, Koffing, Weezing, Jynx, Magmar, and Mew