I would -love- Colours on Steam, its my favourite Sonic game that isn't Sonic 1! Just imagine it'd be some kind of weird effort to bring it to PC. Sonic Generations is a 2011 platform video game developed by Sonic Team and published by Sega for the PlayStation 3, Xbox 360, Nintendo 3DS, and Microsoft Windows.Produced in commemoration of the 20th anniversary of the Sonic the Hedgehog series, the game follows Sonic and his sidekick Tails as they form an alliance with their past selves. Colours is this weird anomaly where it's made especially for the Wii, and everyone knows that wasn't really of the same kind of PC structures as the other consoles, kind of doing it's own thing that a lot of developers didn't want to bother with for cross-platform releases just because it was so different. It was developed on PC like any other game, but we at least know proper PC builds of Unleashed (as can be seen in a bunch of development shots, like this one ), Generations and now Lost World exist and only really had to be appropiately tweaked for the PS3, 360 and Wii U.
Aside from their big lighting one (the Hedgehog Engine) only being partially incorporated and used for the eyes, from what I recall of hacking discussion? I'd love to see a Steam release, but it's important to note it's not made on the same sort of engines that Unleashed, Generations and Lost World are made on.