When you are selecting your vehicle, press the R button to change the vehicle's color! Each vehicle has 2 colors to choose from, except the N64 controller can choose from 6 deferent colors!
To race as one of four secret cars, finish a race with the time exactly 64:00. Since it has to be exact by the 100th getting the any of the secret cars is a matter of luck. Repeate this to get the other secret cars.
To do this trick you must have two controllers and very flexible fingers. Using controller 2, go to the title screen. Press and hold the D-pad Up. At the same time (still using controller 2), press and hold R+L+Z+C down, then release them all. Next, press the Start button on controller 1; the extra tracks and vehicles will then reveal themselves.
While at the starting line, press and hold the A and B buttons on your controller. The announcer will say "Set, Ready, Go!". Right after the announcer says "Ready," release the B button; you should blast off to a turbo start.
These tend to be a little trickier than the turbo start. It's all a matter of timing. To turbo during the race, you must be holding down the A button (for acceleration). Next, make either a hard left or right while holding the Z button, then release both buttons. Immediately after releasing the buttons, tap the A button once or repeatedly. Your speed and vehicle temp. should increase. Keep in mind you have to do this quicly in order for it to be successful, and it may take a few attempts to master. Using the turbo feature can be a big part of winning. You should try to turbo as often as possible without overheating.; it is much more effective around turns.