From Andy Babiuk's Beatles Gear book (page 157) quoting Harrison:
"...But those were the early days and we where lucky to have anything when we started out. But anyway, I decided to get a Strat and John decided he'd get one two. So we sent out our roadie, Mal Evans, said go and get us two Strats. And he came back with two of them, pale blue ones. Straight away we used them on the album we were making at the time, which was Rubber Soul - I played it a lot on that album, most noticeably the solo on "Nowhere Man" which John and I played in unison"