At the main menu, hold L + R + Left Analog-stick + Up + Back. Press Right Analog-stick to change the value of the numbers that appear on screen, then start a new game or resume a saved game to view the corresponding costume.
 
Result Code
Original outfit and hair color 0000:0000
Blackbeard in purple 0000:0001
Red hair with red and orange bikini 0000:0010
Blue hair with orange and red bikini 0000:0011
Tan, brown hair, orange and yellow bikini 0000:0100
Blonde hair, orange and yellow bikini 0000:0101
Blonde hair, pink bikini 0000:0110
Blue hair, shiny silver bikini 0000:0111
Red hair, black bikini, black stockings 0000:1000
Pink hair, shiny black body suit 0000:1001
Blue hair, shiny copper body suit 0000:1010
Purple hair, shiny silver body suit 0000:1011