For any you people were wondering why Casino Night, Mushroom Hill, Emerald Coast, Radical Highway, Water Palace, and Tropical Resort was in the medley; they were part of the 3DS version of Sonic Generations
(I know this is an "old" comment, but I want to clarify something) Actually, both versions of Tropical resort are the ones used, being the DS one for the classic Sonic and the Wii one for the Modern one, even up to the part of the credits of the 3DS version show photos of BOTH versions (although from the DS it is only 1 lmao), therefore he could use any of the 2 versions of Sonic Colors (Although I am not going to deny that it would be better to use the version of DS).