Your magic COLOUR CHANGE HANKY is a trick hanky. If you take a close look at the hanky you will be able to pull down on the hanky whilst holding the secret colour that is sticking out of one end of the hanky.
Be sure during the performance not to expose the tricky end. Your hand should cover the tricky end where the secret hankies are located at all times.
The hankies will turn inside out by gently pulling down on them and the metal ring that is sewn in the hanky.