The song is a twelve-bar blues in the country blues style. When writing "For You Blue", Harrison was partly influenced by his stay with Bob Dylan and the Band in Woodstock over November–December 1968. Whereas that visit had been a musically rewarding experience for Harrison, the Beatles first worked on the song amid an atmosphere of discord, during the filmed rehearsals that made up part of the Let It Be documentary film. Recorded at the group's Apple Studio in London in late January 1969, the song includes a lap steel guitar part played by John Lennon. Among music critics, some have admired the track for its lighthearted qualities and as a good band performance. Other commentators identify it as an inconsequential song, particularly in relation to some of the Harrison compositions that his bandmates rejected over the Let It Be period.
In 1976, Capitol Records included "For You Blue" on the compilation album The Best of George Harrison. An alternative take of the track appeared on the Beatles' 1996 compilation Anthology 3. A live version recorded during Harrison's 1974 North American tour received a limited release on the Songs by George Harrison EP in 1988. Paul McCartney performed the song at the Concert for George in November 2002, a year after Harrison's death.
George Harrison wrote "For You Blue" in late 1968 as a love song to his wife Pattie Boyd. In his autobiography, I, Me, Mine, he describes the composition as "a simple twelve-bar song following all the normal principles except it's happy-go-lucky!" The song was partly influenced by Harrison's recent stay in Woodstock in upstate New York, where he had collaborated with Bob Dylan and jammed with the Band. The visit allowed Harrison to experience a musical camaraderie that contrasted with the tense atmosphere in the Beatles over much of 1968, particularly during the recording of their self-titled double album (also known as "the White Album"). In addition, the creative equality Harrison enjoyed among these musicians, as on his recent collaborations with Eric Clapton, contrasted with the continued dominance of John Lennon and Paul McCartney in the Beatles during a period when Harrison was emerging as a prolific songwriter.
"For You Blue" is a country blues song in the musical key of D. Aside from the introduction, it is one of the few original songs by the Beatles in which every section follows the twelve-bar blues (I-IV-V) pattern. The five-bar introduction deviates from the pattern due to its length and the inclusion of what musicologist Alan Pollack terms a "V-of-V" chord – namely, E7 in the home key. On the Beatles' recording, Harrison performs this opening section alone, playing a series of "elegant introductory hammer-ons", according to musicologist Walter Everett. The song's bluesy feel is accentuated by the addition to the minor pentatonic scale of a ♭7 note on each of the I (D7), IV (G7) and V (A7) chords. Harrison opts for a popular variant within the twelve-bar blues formula, by moving briefly to the IV chord for the second bar, rather than remaining on I until the fifth bar.
The composition comprises two verses, a two-round instrumental break, and two further verses. In his lyrics, Harrison unashamedly states his love for Boyd; Pollack describes the message as "unusually unmuddled romantic euphoria". Early in the song, Harrison tells her, "I loved you from the moment I saw you", and by the last verse, in the description of author Ian Inglis, " 'sweet and lovely' personality makes her irresistible ... he now loves her 'more than ever.'"