The Blue Green Switch is an e-Reader card for use with Super Mario Advance 4: Super Mario Bros. 3. It was included in the Series 2 set of cards. Although technically a Power-Up card, it was labeled as a "Game Level" card. It can only be used in the main game.
Once the Blue Green Switch is scanned, grass with turnips below appears all throughout the main game, and Mario can pluck them from the ground and throw them at enemies, just like in Super Mario Bros. 2.
