Fancy - red AND white cobs.
According to Stana Claus, posting on straightdope.com in 2002:
Just so you know, some varieties of corn have a dark reddish cob while others have more of a whitish colored cob. When I was but a wee child I was told by my beloved grandfather that the proper outhouse technique required "two reds and a white". The red cobs (apparently more readily available, at least in that locale) were used for bulk removal, and the white was used to determine if the job was sufficiently done. Surely, my grandfather wouldn't have lied to a small impressionable child about such a thing!