Super Smash Brothers - Nothin' personnel, kid

The closest we'll get to have Sonic OCs in the game.

Pac-Man has it worse, and I don't think third-parties are allowed to have drastic color swaps.

Mega Man gets a pass because all of his colors are from his games, but in Sonic and Pac-Man's case, their color is a big part of their identity. If it's not blue, it's not Sonic, and if it's not yellow, it's not Pac-Man.