In the official E3 press release Nintendo announced release date for Mario: Color Splash will be October 7th.

You can check out gamplay footage of Mario: Color Splash during Wednesdays Nintendo Treehouse.

The final day of Nintendo Treehouse: Live begins at 10 a.m. PT on Wednesday, June 15, and will primarily offer a showcase of previously announced Wii U and Nintendo 3DS games, including Tokyo Mirage Sessions #FE (June 24), Monster Hunter Generations from Capcom (July 15), Paper Mario: Color Splash (Oct. 7) and Dragon Quest VII: Fragments of the Forgotten Past (2016).