From the back cover of the US Nintendo DS edition
"Welcome to Dr. Eggman's Incredible Interstellar Amusement Park!
Can Sonic's new Color Powers stop Dr. Eggman's plans to take over the universe, and free the captured alien Wisps from his cosmic theme park?
New powers access hidden areas... and perform new moves!
Adrenaline pumping super speed!
Explore new environments!
Also race against your friends!"
"The Nintendo DS version is largely a side-scroller that takes advantage of the dual screens of the handheld, similar to the Sonic Rush DS games."
Source: Wikipedia, "Sonic Colors", available under the CC-BY-SA License.