Rainbow Sushi is a main dish. It was originally a regular dish but is now limited (disappears if it hasn't been leveled by February 1, 2011). It begins at level 0. To achieve level 10 in this dish, you need 20 tuna and 10 rice. In addition, you must master Vegetarian Platter before you can level up Rainbow Sushi.
Mastering Rainbow Sushi unlocks Idols screen and round coffee tables for your Karaoke Bar (+2GP per customer). Mastering Rainbow Sushi also unlocks Mega Fruit Sorbet.