Continuity mistake: Hugo Dore goes over to the bookshelf empty-handed; in the next shot, he picks up a book and now has a cup of coffee in his right hand. In the next shot of him giving Joey Ross the book, the cup has gone again. (00:36:00)
Continuity mistake: Hugo puts his mug down on the table before going to fetch a book. As turns back from the shelf, the mug is back in his hand, and then as he crosses the room, it is gone again. (00:35:55)
Chosen answer: It was a bottle of turpentine.
Methylated spirit, always coloured purple.