Red Light is the third studio album by South Korean girl group f(x), released on July 7, 2014, by S.M. Entertainment. It reached number 1 on the Gaon weekly album chart and had two promotional singles, "Red Light" and "Milk". This is the last album to feature member Sulli, who left the group one year after the album's release.
The Red Light album has a dark and eerie concept, which f(x) said they liked. Krystal added that she likes this concept because she's often given roles that make her look pretty, and just this once she wanted something that would make her look darker and different.
Naver describes the album's title track, "Red Light", as a "blast of urban rhythm bit, reversal in electrohouse genre". The lyrics talk about capturing great moments, stop and reconsider what is important in life. Also, it is a message, using a “red Light” to symbolize the warning, that is expressed in an eye-catching way. Kenzie, penned the lyrics for the song and Maegan Cottone of Phrased Differently, Daniel Ullmann, Bryan Jarett, Allison Kaplan, and Sherry St. Germain were credited for the song's music. It was produced by Lee Soo-Man and Casper & B. F(x) member Amber Liu describes the song's dance as the "most passionate" and "most dynamic". Member Luna stated that the song's genre fit with their aim for a slightly intense but feminine image.
The title track "Red Light" impacted Korean Broadcasting System's "K-Pop Connection" radio on July 8, 2014.