Magician clearly shows a mixed up Rubik's Cube to the audience he then puts it in an empty box. After a magical gesture, the Rubik's Cube is taken from the box and is now solved! Each side of the cube has a solid colour and is shown on all of its sides to the audience.
Then for the finale the magician puts the cube back into the empty box again. This time, when the Rubik cube is removed from the box, the cube has magically changed to a solid yellow cube! Can be shown before and after each change! Easy to perform!
This is perfect for children's entertainers and makes a super routine if you use, for example, a change bag and six coloured silks matching the colours on the cube and allow a child to 'select' a colour for the final change.