It has been called "the prettiest and most uncharacteristic song" that Mick Jagger and Keith Richards wrote for the Stones, although somewhat ambiguous in intention. It features rich lyricism, vibrant piano by Nicky Hopkins and Brian Jones' use of the Mellotron. The second verse goes:

Have you seen her all in gold,
Like a queen in days of old?
She shoots colours all around
like a sunset going down.
Have you seen a lady fairer?

John Paul Jones, later of Led Zeppelin, arranged the strings of this song during his session days. Backing vocals were provided by the entire band except for Charlie Watts. The lyrics in the chorus share the phrase "she comes in colours" with the song of that title by Love, released in December 1966.

The song begins with the piano playing an ascending scale, which returns throughout the song as a recurring motif. This motif is developed by the celesta and strings in the middle 8. Humorous and ambiguous devices are used, such as when the strings play out-of-tune and off-key towards the end of the song, and when the other Stones sing their "La La's" like little children. The song ends on an unusual sour electric guitar chord combined with bassoon (most likely performed on the Mellotron by Brian Jones).

"She's a Rainbow" was released as a single in December 1967 and went to No. 25 in the US. It has regularly featured on Stones' hits compilations, including Through the Past, Darkly (Big Hits Vol. 2) (1969), More Hot Rocks (Big Hits & Fazed Cookies) (1972), 30 Greatest Hits (1977), Singles Collection: The London Years (1989), Forty Licks (2002), and GRRR! (2012). It was performed occasionally on the 1997–98 Bridges to Babylon Tour. Apple Inc. used this song in an advertisement for the iMac G3. Later Sony used the song in an advert for BRAVIA.

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Wikipedia