if you look deep inside the Rom of firered, you can see that there are sprites in the game of the final evos of the three starters that are large enough to fit on the title screen of the game and look good. there is a Charizard, a Vensaur, a Blastoise, aaaand, a pikachu. what this tells me, is that leafgreen was most likely supposed to be a waterblue or something like that in the states in the states, but nintendo got lazy. it also says that they were planning on making a yellow remake, but abandoned it because they were too busy with either emerald, mystery dungeon, D/P, or a combination of those four