From the Super Mario Wiki
Prisma Cardware (referred to as the Card Shop in the online manual) is a Battle Card shop in Paper Mario: Color Splash. It can be found in the blue district in Port Prisma. The shop is opened after Mario repaints the owner, a Blue Toad. As the player progresses in the game, more cards become available. A red Toad appears outside of the shop, and tells Mario whenever a new card is available.