Paper Mario: Color Splash is the first of the Paper Mario series to be released on the Wii U. The story starts with Princess Peach and Mario receiving a letter from Prism Island, which they find out is a color-drained Toad. This causes Mario, Peach and another Toad to set sail for Prism Island. Upon arriving, Mario finds a hammer and uses it to reach the town square, that is deserted and full of elements whose colors have been drained. Toad then heads off, while Mario and Peach, after activating an emergency mechanism, meet Huey, a mysterious 3D talking paint bucket. A scream is heard and Mario, Huey, and Princess Peach quickly head over to the sound only to find a red Shy Guy with a straw, called a Slurp Guy, draining the color from Toad.
Toad gives some Battle cards to Mario and then the Slurp Guy fully drains his colors. Huey then asks Mario to squeeze him into paper form in order to obtain colors from his blood, his sweat, and his tears. The colors are used to battle the Slurp Guy and two Shy Guys that came to his assistance. After the battle the colors from Huey are used to return Toad to color using Mario's Paint Hammer. After Huey informs Mario of the Big Paint Stars which inhabited the main plaza's colored fountain he points out towards a red Paint Star on top of the main plaza tower, mistaken it for a BIG Paint Star. As soon as they reach the Mini Paint Star, they see an airship carrying a giant bucket of red paint that was stolen by the Slurp Guys.
The combat ability displayed by Mario and his free movements through the overworld are similar to Paper Mario: Sticker Star, through free combat by encounters in the overworld avoiding or engaging enemies at will. When engaging in battle Battle Cards are used to engage the enemies, which either are fully colorized or need to be painted to fully use their effect. Once used cards or cards that are not used in battle (but are selected in the progress) are discarded, but can be bought back at a shop in Prism Island. Three different types of Battle Cards can be used: Hammer Attacks, Jump Attacks and Thing Cards.
Thing cards are 3D things which Mario can find in the field and squeeze out the colors from, to be used in battle and to solve puzzles. Also there is a similar move like "Paperization", used in Paper Mario: Sticker Star, called "Cutout" in order to cut part of the courses to create shortcuts, place Thing Cards or extract various items.
During the adventure of Mario and Huey, the amount of cards to be put in play, the amount of paint the Paint Hammer holds and the maximum HP of Mario can be increased. The maximum HP of Mario is increased only when one of the six Big Paint Stars is collected and returned to the fountain.
The game became the subject of a minor online controversy back in 2016, when demo footage was shown during a livestream event at E3. It showed a Toad inviting Mario to participate in a mini-game, involving keeping track of "Five Fun Guys" who keep shuffling around; after Mario reveals that the mini-game is rigged, the Toad says: "I can see the headline now: ‘Shufflegate: Exposed!’". This drew the ire of Zoe Quinn, an indie game developer. Quinn was convinced that the quoted phrases were references to Gamergate, a controversial online campaign which involved accusations that she had slept with "five guys" from the videogame journalism community in exchange for positive coverage. On June 22nd Quinn complained on Twitter that Nintendo had turned her "suffering into a fucking joke". Multiple Twitter users supported her and spoke negatively of Nintendo.
Nintendo released a statement on June 23rd, stating that the jokes were never meant to be a reference to "an online hate campaign", but were simply a shout-out to the "Fungi Fun Guys" from Mario Party 8 and to the Watergate scandal, respectively. On June 24th, Quinn assented on Twitter that the jokes were, in fact, "an extremely specific unfortunate coincidence."