From the Super Mario Wiki
Paint Guys are a type of Shy Guy that appears in the game Paper Mario: Sticker Star. Paint Guys are Shy Guys that carry a can of yellow paint into battle and are usually accompanied by Snifits, Clip Guys, and Ninjis. If the Paint Guy still has a paint can over its head, it will attempt to push Mario and try to cover the screen with yellow paint. Rapidy pressing the button or repeatedly touching the touch screen is the only way to prevent this from happening. If the player does not do it in enough time, the Paint Guy will cover up important things like the health bars (both the enemies' and Mario's) and Mario's attacks. If the Paint Guy fails to do so, the Paint Guy will go back to its position with its can of paint above its head. However, after each attempt, the speed at which the Paint Guy pushes Mario increases. Once a Paint Guy loses its paint can, it will attack like a normal Shy Guy.
Paint Guys are never seen outside battle, so in order to fight them, Mario would need to go in battle with a Snifit, a Ninji, a Shy Guy or a Piranha Plant.
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