In the movie "The Matrix", I think NEO had already been "red pilled" just by visiting Morpheus. He wasn't surprised and didn't deny it when he was told "You are a slave, Neo." The blue pill was the antidote for where he already was, which is contentment within his slavehood, the red pill is continuing on the same path, seeing "how deep the rabbit hole goes." otherwise.... "I don't want to remember nothing... nothing! And I wanna be rich, someone important."