Colouring Book Colouring Book
An excellent example of this popular effect.
The magician flicks through the completely blank pages of a colouring book. Claiming that you need to be a magician to see the pictures, the children are asked to imagine that they are. The pages are flicked again and are now seen to be full of line drawings. The audience is asked to think of different colours and throw the colours at the book. After much by-play, the book is now shown to be full of colurful pictures.