In the hands of your little blue scarf. Show the left hand, then squeeze your hand into a fist and slowly poured in his handkerchief your right. Then on the other side of the fist pull out a handkerchief, but... red. Open the fist - it is empty.
About the props. The secret of focus in a tiny tube. To make it from thin sheet metal or of plastic. The length of the tube of about 50 mm Diameter adjust such that the tube were freely put on your thumb. In the center it around the diameter, do a few small holes. They need to sew into a tube a small bag of matter. To the tube was not noticeable on the finger with a small distance, color it in flesh color.
Before the demonstration of focus include in the bag a red handkerchief, and the tube is put on the thumb of the right hand. In the same hand, take the blue handkerchief. Show the audience left hand - there's nothing there. And then, masking his hand a blue handkerchief, quickly remove the tube and with a red handkerchief leave in his left hand. It is now clear that blue scarf you filled in a tube, and he, pushing red, takes his place. Once out of the hand will seem red handkerchief again put the tube on your finger, expand and show it to the audience on both sides.