T: Story Begins With T cheats and cheat codes for Playstation

Change window color
While palying a game, wait until the message window appears. Then,
hold Select + Triangle + L1, L2, R1 or R2 buttons. Keep held these
buttons and press Down or Up to change the color value. R1 controls
blue, L2 controls green, L1 controls red and R2 controls all
three values.

Change main characters
Press Right, Left, Right, Down, Up, Up at the title screen.
There is a number at the upper left corner of the screen.
Change the number to play as different characters.