I do like the idea of "white face" paint - easily found in costume/party shops with the Halloween facepaint section...See also, from www.ultimatehaunt.com:
Three Colour Ghost and Skull
£3.50 + P&P
Three colours to change you into a skull or ghost. Pale skin and black eyes haunt the night.
Colours: White, grass green and black.
These water based products wash off with soap and water but may stain fabrics. All cosmetics can, on rare occaisions, cause allergic reactions. Use within 18 months of opening.
3 X 2ml water-based face paints and applicator brush.Adult supervision advised.