1997 (Pocket Monsters 2)
This logo was used during the initial planning stages of the game.
1998 (Pocket Monsters Gold & Silver)
In 1998, when the games were re-announced, the games were renamed Gold & Silver respectively and the "2" was dropped.
1999 (Pocket Monsters Silver)
This is the final version of the logo used when the game was finally released in 1999.