Waters told a 1970 crowd it was about Ibiza
Green Is The Colour is the quiet song on More, the soundtrack Pink Floyd wrote for Barbet Schroeder’s film. They recorded the album at Pye Studios in London in early 1969, with engineer Brian Humphries, and EMI Columbia released it in Britain on 13 June 1969. It was the first record the band produced without Norman Smith at the desk, and the first full album after Syd Barrett had left. Roger Waters wrote this track. David Gilmour sings it and plays acoustic guitar.
The arrangement is small. Richard Wright plays piano and Farfisa organ. Waters plays bass. Over the top sits a tin whistle, played by Lindy Mason, Nick Mason’s wife at the time. The track runs just under three minutes. In a 1970 stage introduction Waters told the crowd it was about being on Ibiza, which is where Schroeder set the film. On the record the song stays pastoral. It does not try to be the rest of the soundtrack, which also has the hard riff of The Nile Song and long instrumentals.
Live, they did not keep it that small. From 1969 through 1970 it was a slower electric piece, Wright’s organ running underneath, and it almost always fell straight into Careful with That Axe, Eugene. Gilmour would scat over the guitar on the way out. In the 1969 show they called The Man and The Journey, Green Is The Colour was renamed The Beginning, and the axe piece that followed was Beset by Creatures of the Deep.
Schroeder wanted the music inside the scenes, coming off a radio, a party, or a cassette, not a score pasted on after the cut. Pink Floyd had already had pieces set beside pictures, including The Committee and parts of Zabriskie Point. More was the first time they wrote a full film score to order, and they did it in about a week at Pye. Hipgnosis handled the sleeve. Gilmour’s vocal on this track is dry and close. The tin whistle is the only player from outside the band. The album track is the one on the EMI Columbia LP. The live medley with the axe is a different piece of work, slower, and electric.
This is a song about being on Ibiza.
(Roger Waters, stage introduction, 29 April 1970)

They played it less often in 1971. The last time the four of them did it on a Pink Floyd tour was the short run through Japan and Australia in August 1971. By then Meddle was the record they were finishing, and this Ibiza ballad was already an older song from a film job done in a short London session.
More is a soundtrack, not a manifesto. Green Is The Colour is the part that stayed gentle on tape: acoustic guitar, organ, a tin whistle, and a segue into the axe that only appeared once they took it on stage. Nick Mason’s Saucerful of Secrets picked the song up again years later. The 1969 recording is the one that counts.