The colorized version of the “Artificial Humans & Cell arc” of the Dragon Ball manga is up for pre-order in the Japanese iBookstore (though not yet via Shueisha’s “Jump BOOK Store!” app), and will officially go live 04 September 2013.
The digital version of the arc will run for eight volumes and cover chapters 330 to 420. Preview downloads are available, and now include a proper table of contents. Depending on the service used, the price ranges between ¥450 and ¥480.
Shueisha has not announced any print volumes beyond the currently-released Saiyan and Freeza arcs.
Viz is currently publishing the digital version of the “Z”-era “Full Color Comics” in English as a single chapter in each issue of their own Weekly Shonen Jump with a print edition coming in February 2014.
Additionally, Akira Toriyama’s on-again/off-again spin-off and parody series Neko Majin (originally and sporadically published as single chapters between 1999 and 2005) has actually been available on the service since this spring! The same ¥450-480 gets you all eight chapters from the various sub-series (two chapters of Neko Majin ga Iru, one chapter of Neko Majin Mike, and five chapters of Neko Majin Z). Most interestingly, the entirety of the series has been colorized a la the Dragon Ball “Full Color Comics”. All title pages and any special color pages remain the same as their original printings (both in magazines and in its kanzenban release from 2005), but all additional black-and-white pages have been updated with new colorized versions.
The final chapter of the spin-off — the fifth Neko Majin Z chapter — was printed in English (without its chapter number) by Viz in their October 2007 issue of Shonen Jump. It has not yet otherwise been officially made available in either print or digital versions.