From BrodyQat, whose infamous desaturated Santa outfit made her the toast of the Internet, advice on how to make yourself a monochrome costume:
You have to think in shades of gray, not black & white. And all your grays need to complement each other, which is freaking HARD. There's blue-grays, red-grays, etc. Find neutral ones, use mainly those and accent with black & white. (Wearing all black & white is not the same as looking desaturated).
Once you've matched all your grays for your outfit, you then need to match a skin-tone gray body paint. By 'skin tone' I mean it looks like your particular shade of skin tone, but gray. I recommend only Kryolan brand aquacolor body paint, they have lots of shades and coverage is amazing. Match colors in person if you're lucky enough to have a vendor near you. I wouldn't chance it looking at shades online, honestly.
Line your eyes top and bottom with dark gray eyeliner BEFORE you paint your face & exposed skinparts. Then shade back in your eyebrows so you don't look like Amanda Palmer before she breaks out the eyebrow Sharpie.
(via Super Punch)
(Image: Ben Zero)