If the player talks to the Colorful Screw Exchange person after collecting all the Colorful Screws in Lumiose City and buying every Canari plush, the player will be rewarded with a "giant Canari plush" decor for their room in Hotel Z.
The Colorful Screw cannot be given to a Pokémon to hold.
A colorful screw. These screws have been left here and there around Lumiose City, and the staff at Racine Construction will trade you goods in exchange for them.
