Well, I'm pretty sure Red Toad is the ACTUAL Toad, just wearing a different-coloured vest (laundry day, maybe?), and Blue Toad appears to be in the game for whatever reason. Yellow Toad is the main host of the game, and Green Toad sort of acts like a checkpoint. When you reach him, he gives out the current standings, and helps out the last player in some way, similar to the last 5 turns from previous Mario Parties, but I forgot how he helps you. This is all seen in a gameplay video by Nintendo.de. Too bad Purple Toad seems to be skipping out on this game too, he's always forgotten. :\