Apparently Methylene Blue will turn your urine blue or green depending on how much you took. I've done some research and the only risks seem to be for the rare chance of an allergy or if the person is pregnant, the effects last a few days. It supposedly has a light bitter taste so a good enough amount can be added to a coke really quick and the person won't notice.
So next time your at the fish store, give this stuff a second, diabolical look.:sgrin:
So next time your at the fish store, give this stuff a second, diabolical look.:sgrin: