Au contraire, see they've managed to find a way to be witty and clever about it.
Or so they clearly think, at least.
You're locked into an exact pool of four colors themed after a character/Sonic game stage and that's what you get.
Most of the real custom deets involve stuff like the three alternate vehicle shape sets for each character and their gold counterparts, vinyl prints, horns (oh hey Starbound), apparent glow features that I must not have unlocked or something, and oddly enough the material types of each patch of color, aka plastic, metal, paint etc. I managed to take the toylike sheen all the cars have off of Tails' car playing around with it, but you can flip it around and make your car's paint job -extra- shiny as you so please.