This January 1969 recoding features the song’s author George Harrison on vocal and acoustic guitar, John Lennon on lap steel guitar, Paul McCartney on piano and Ringo as usual on drums.
George: Does this guitar sound in tune?
George Martin: It’s good enough for skiffle.
About For You Blue from Wikipedia:
The song is in the key of D and is one of the few original Beatles songs in which every section follows a classic twelve bar blues (I-IV-V) pattern. Indeed, in his vocal at 1.18 secs Harrison states this is “the twelve bar blues.” The ‘bluesy’ feel to the song is accentuated by the addition to the blues-based minor pentatonic scale (I-flat3-4-5-flat7) of a flat7 on each of the I (D7), IV (G7) and V (A7) chords. A variation from the twelve bar blues pattern is the insertion of a IV7 (G7) chord on “lovely girl” in the opening I (D7) verse bar.