This is the only known copy of The Beatles (aka The White Album) pressed on Blue vinyl. It was made in 1978 by Colin Mcdonald who was working at the pressing plant, having just finished a run of Linda Ronstadt's Bayou In Blue on blue vinyl, McDonald popped in the coloured vinyl to make himself a bespoke copy. He since met Paul McCartney who signed it for him, making this a very valuable record.
This isn't the first time that a one off copy has surfaced, it wasn't unusual for people working the presses to make a "souvenir" that would turn up leaving collectors scratching their heads. These are extremely rare however, in a large part to the dubious legality (pressing a record and taking it home is theft).
So three cheers to Colin, for giving myself and millions of others a chance to see this wonderful example.