The red pill and blue pill represent a choice between the willingness to learn a potentially unsettling or life-changing truth by taking the red pill or remaining in the contented experience of ordinary reality with the blue pill. The terms originate from the 1999 film The Matrix.
In The Matrix
In the film The Matrix, the main character Neo (played by Keanu Reeves) is offered the choice between a red pill and a blue pill by rebel leader Morpheus (played by Laurence Fishburne). Morpheus says "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." It is implied that the blue pill is a sedative that would cause Neo to think that all his most recent experiences were a hallucination, so that he can go back to living in the Matrix's simulated reality. The red pill, on the other hand, serves as a "location device" to locate the subject's body in the real world and to prepare them to be "unplugged" from the Matrix.
Neo takes the red pill and awakens in the real world, where he is forcibly ejected from the liquid-filled chamber in which he has obliviously been lying. After his rescue and convalescence aboard Morpheus's ship, Morpheus shows him the true nature of the Matrix: a detailed computer simulation of Earth at the end of the 20th century (the actual year, though not known for sure, is suggested within the original movie to be approximately 200 years later, though it is revealed through sequels The Matrix Reloaded, The Matrix Revolutions and The Animatrix that at least 700 years have passed). It has been created to keep the minds of humans docile while their bodies are stored in massive power plants, their body heat and bioelectricity consumed as power by the sentient machines that have enslaved them.
Later Matrix films
In a 2012 interview, Lana Wachowski said:
In the 2021 film The Matrix Resurrections, the Analyst uses blue pills to keep Neo's true memories suppressed in the guise of therapy sessions. Later, Neo takes another red pill before being freed from the Matrix once again by Bugs and her crew. In Trinity's case, she does not have to take the red pill again because of the way that Sati is freeing her from the Matrix. The red pills also allow friendly programs to leave the Matrix, as seen with the program version of Morpheus.
Analysis
An essay written by Russell Blackford discusses the red and blue pills, questioning whether if a person were fully informed they would take the red pill, opting for the real world, believing that the choice of physical reality over a digital simulation is not so beneficial as to be valid for all people. Both Neo and another character, Cypher (Joe Pantoliano), take the red pill over the blue pill, though later in the first Matrix film, the latter demonstrates regret for having made that choice, saying that if Morpheus fully informed him of the situation, Cypher would have told him to "shove the red pill right up [his] ass." When Cypher subsequently makes a deal with the machines to return to the Matrix and forget everything he had learned, he says, "Ignorance is bliss." Blackford argues that the Matrix films set things up so that even if Neo fails, the taking of the red pill is worthwhile because he lives and dies authentically. Blackford and science-fiction writer James Patrick Kelly feel that The Matrix stacks the deck against machines and their simulated world.
Matrix Warrior: Being the One author Jake Horsley compared the red pill to LSD, citing a scene where Neo forms his own world outside of the Matrix. When he asks Morpheus if he could return, Morpheus responds by asking him if he would want to. Horsley also describes the blue pill as addictive, calling The Matrix series a continuous series of choices between taking the blue pill and not taking it. He adds that the habits and routines of people inside the Matrix are merely the people dosing themselves with the blue pill. While he describes the blue pill as a common thing, he states that the red pill is one of a kind, and something someone may not even find.