“This is your last chance. After this, there is no turning back. You take the blue pill – the story ends, you wake up in your bed and believe whatever you want to believe. You take the red pill – you stay in Wonderland and I show you how deep the rabbit-hole goes.”
The terms red pill and its opposite, blue pill, are pop culture terms that have become a common metaphor for the choice between the blissful ignorance of illusion (blue) and embracing the sometimes painful truth of reality (red). The terms were popularized in science fiction culture via the 1999 film The Matrix. The movie relies on the premise that an artificial reality that is advanced enough will be indistinguishable from reality and that no test exists that can conclusively prove that reality is not a simulation. This ties in closely with the skeptical idea that the everyday world is illusory, a simulated reality.
In the movie, a “red pill” is the term used to describe a human who has been freed from the Matrix, a fictional computer-generated world set in 1999 and a “blue pill” refers to a human still connected to the Matrix.