Color Change:
On the Player Select screen, highlight your player and press SELECT+START simultaneously to change his or her colors.
Extra Fighters:
Turn off the power; press and hold ALL the buttons (A+B+X+Y +[L]+[R]+SELECT+START), turn on the power and continue holding the buttons until Press Start appears. Release the buttons and begin the game. At the Character Select screen you will now be able to select one of the extra fighters.