You can finally play the original Pokémon games on your 3DS, but Nintendo’s handheld has a few secret ways for you to maximize your nostalgia.
If you buy Pokémon Red, Blue, or Yellow from the 3DS eShop, you can play them in their original resolution with a virtual Game Boy border. With a few button presses, you can also play Red and Blue in their original pea-soup green color. These are tools built into the 3DS, and they work with every Game Boy game available for the Virtual Console.
Here’s how to activate these special modes:
Original resolution and Game Boy border:
Go to your 3DS’s main menu.
Find Pokémon Red, Blue, or Yellow.
Hold down Select or Start.
Tap on the game or press A to boot it up.
This will cause the game to take up the same number of pixels that the original Game Boy system had. It will also put a Game Boy (or Game Boy Color in the case of Yellow) around the action.