Interesting - can you hear where the difference is?
My copies of Aftermath have it as: 3:22 on the stereo and 3:24 on the mono
It is 3:44 on the London Singles collection.
Wiki/my notes from the complete Stones mp3 set says
"Paint It Black"
Single by the Rolling Stones
B-side "Stupid Girl" (US) "Long, Long While" (UK)
Released 6 May 1966 (US) 13 May 1966 (UK)
Recorded 6–9 March 1966 at RCA, Hollywood, California
Length 3:19 (mono single mix*) 3:22 (stereo album mix)
Label Decca (UK) London (US)
Producer Andrew Loog Oldham
*The mono single edit appears only on the Mono Box Set edition of the US version of Aftermath. All compilations have the full 3:44, longer fade out version. The 3.22 edit appears only in its stereo form on Hot Rocks (and the stereo mix of the US Aftermath) . I have sourced the correct mono single mix and edit here.
Mick Jagger – lead vocals
Keith Richards – electric and acoustic guitars, backing vocals
Brian Jones – sitar
Bill Wyman – bass
Charlie Watts – drums
"Paint It, Black" is credited to songwriting partnership of Mick Jagger and Keith Richards, it was first released as a single on 6 May 1966 and was later included as the opening track to the US version of their 1966 album, Aftermath.....etc
The Complete Jah Bob Mp3 set now available in the usual place, should you want one.