People seem to generally think of this as a really good Sonic game, but ehhh... I think it's just okay. It's just that each zone has six acts, but there's usually only one or two that are actually fun (with the exception of Planet Wisp, probably the best time I had playing the game, and also the absolute best atmosphere and music, besides just having the best gameplay). The majority of the levels feature a lot of boring 2D platforming that Sonic's controls just don't feel very well suited for. There is one stage that is literally just 40 seconds of quick stepping. A good chunk of Sonic Colors just feels very unsubstantial.
The Wisps are cute, and as a gameplay mechanic, they're fine enough. The story they're wrapped up in is also sort of just okay. The characters are just so incredibly annoying in every cutscene though that it's hard to want to hear any more about the story. The final boss felt very creative in the way it used all the Wisp powers against you, but it was over too quick to build on that idea much at all.
Really the one thing I can gush about with Sonic Colors is the entire atmosphere of Planet Wisp. The beautiful music, the way you can ominously see the tractor beam generator in the background as you run around. The clashing natural landscape with Eggman's machinery makes it really feel like a planet you want to save, whereas the others all felt uninhabited (you only ever saw Eggman's robots in each place, no signs of life of anything).
I guess I'll leave the review on that note, as I don't really have a lot I want to say about the game. Not frustrating like Sonic UnWiished, but just incredibly boring most of the way through.