You're best off running some Google image searches for the JGTC and other racing leagues. That'll give you an idea for overall composition.

As far as major color swaths go (like the blue & yellow Spoon cars) the cheapest way is to use a vinyl wrap for a section of the car. That said, it's not the most durable or fade-resistant way.

Ultimately, you're going to need to work with a vinyl print shop to print the stickers and in the case of a full body wrap, do the installation.