Nintendo uses a Blue Shell.
Mario Kart 8 is probably the biggest release yet for the Wii U (and, along with the upcoming Super Smash Bros., represents the best shot the flailing console has at survival). So naturally, Nintendo are going to push the game with everything that they have got. And sure enough, they have announced a Mario Kart 8 bundle for Europe and Australia, that comes with the Wii U console (32 GB), along with everything that that includes (including a one year subscription to Nintendo Network Premium) and a physical copy of the game (as well as, for some reason, a 7 day subscription to Wii U Karaoke).
The bundle is priced at 299.99€/249.99£/439AU$, and is scheduled to release on May 30, which is when the game itself releases; in addition to this bundle, which will be available at all retailers and stores that still sell the Wii U, the Nintendo UK Web Store is also offering two special themed bundles- a Team Mario bundle (which comes with the console, a physical copy of the game, a Mario hat, a red Wiimote, red Wii Wheel, and a red Wii U Pad), and a Team Luigi bundle (same stuff, but green).
If you haven’t yet picked up the Wii U, now is the best time to pick one up- it’s cheap, the games are there, and there’s more incoming. Whether Nintendo’s Mario Kart gambit with the Wii U plays out remains to be seen, but if this game doesn’t help the system’s performance at retail, there is very little left that will.