Here is a video showing off the brand new multiplayer game play in Sonic Colours for the Wii. You will unlock multiplayer levels as you collect hidden red rings in the single player zones.
Multiplayer is a Co-op affair with where you use wisp powers to help each other get though the level. There is also a hint of competitiveness to keep things exciting.
I personally hope they also bring back a VS racing mode like in the classics or Sonic Adventure 2:Battle.Ad: