The red pill and the blue pill are symbols representing the choice between embracing the uknown truth of reality (red pill) and continuing the safe life in illusion (blue pill).
The terms are derived from the 1999 movie The Matrix.[video] The dilemma can also be found in other sci-fi works, e.g. in the 1990 movie Total Recall, or the comedy-drama The Truman Show. More: en.wikipedia.org.