Several questions regarding hair dye?

This is actually questions in one:

First of all, you probably have heard of a hair dye you can make at home using Kool-Aid mix. I've been told different things about this, like it washes out in a couple washes, or that it stays in for about a month. Has anyone tried this before and do they know how long it takes to come out?

Second, if the Kool-Aid doesn't work, do you know of any recipes that are good for VERY short-term periods of time? (Three or four days)

Third, if neither of those questions apply, do you know of any store-bought hair dyes that will wash out in a few days? I heard about some sort of hair dye from Hot Topic, but I never tried it and I don't know anyone who has.

Thanks.