Unlock monochrome mode: To change the graphics to black and white, type the following cheat code to the Code entry screen at the options menu: "9DE5"
Different Colors: To change the saturation and hue of colors, type the following cheat code to the Code entry screen at the options menu: "B6FC"
Unlock Sketched Graphics: To change the graphics to high contrast black and white type the following cheat code to the Code entry screen at the options menu: "A8D7"