"Red" was composed solely by Robert Fripp. In an analysis of the piece by Andrew Keeling, he describes "Red" as "an instrumental piece scored for electric guitar (multi-tracked in three layers), bass guitar and drums," as well as "one of the more muscular pieces of Robert Fripp's, in particular the deployment of open strings and heavily attacked and syncopated bass and drums." In an online diary from 2012, Robert Fripp speaks about the development of "Red": "A motif; moved from missing piece "Blue" to "Red": the opening and closing theme of "Red" itself. The driving, relentless figure that follows it, and the middle figure played by the basses, weren't enough for a complete piece." Speaking about it in the book accompanying the "" box set, he says, "After we had just recorded the track "Red" in ] ... we played it back and Bill said, 'I don't get it, but if you tell me it's good, I trust you.' ... I said, 'We don't have to use it.' John was in no doubt: 'We'll use it.'" An unused variation of the song's middle section would later emerge in 1983, during the writing rehearsals for "Three of a Perfect Pair". Though it went unused, it finally saw light in 1995, more than two decades later, as the middle section of the instrumental "VROOOM VROOOM" on "THRAK".