In ‘Happy Butterfly Day’ Warhol uses his blotted-line technique and shows an early interest in the repetition of a similar image – a characteristic which would define much of his later work. The vibrant colours were possibly added at one of Warhol’s colouring parties, hosted at the fashionable Serendipity 3 café after it opened in 1954. He would encourage his friends – some of whom would have helped him create the original illustrations - to colour the works with an inventiveness that adds to their whimsical nature. This process looks forward to the production methods of Warhol’s legendary studio, the Factory, in the 1960s.