Cheat Menu:
Start a normal race and pause the game at any time. Go down to 'race statistics' and simultaneously press L1, L2, R1, R2, Select, X, Circle. This should bring up a cheat menu.

Different Colored Cars:
Start a new race and select Begin Career. At the Registration screen enter:
GO BEARS! -- for stock cars
or
GO BRUINS! -- for indy cars
Now check out the car selection screen.....