Aka Manto

One of the most famous bathroom ghosts in Japanese lore. This spirit is one of the main reasons why many are afraid to use the bathroom at night.

Answers & Questions
Aka Manto generally appears as an ominous voice from nowhere but, only if you enter the very last stall. It will ask you a simple question. "Red paper or blue paper?" ((Alternate versions include; Red cape or blue cape, Red vest or blue vest, & red cap or blue cap?))

If you answer blue paper, you will suddenly lose the ability to breath and die of suffication. In some variations a pair of spectral hands appears and strangles you until your face turns blue, or even strings you up and slices you open allowing all the blood to drain from your body.

If you answer red paper, your throat will suddenly be slit. A number of variations include, being torn or cut to peaces, having the skin pealed off of your back, chest, or both, and other various dismemberments.

A much more humerous answer would be to answer "Yello paper." In which you are forced into the toilet you just used and drowned in your fluids.

Solution
Saying nothing to the spirit is said to result in one being dragged to hell or the netherworld.

The only way to escape with your life is to simply answer "No paper thank you." or a simular variation.