He passes his hand over the pair of Silks, and they change to two silks of entirely different colors (say Blue and Orange).
The effect can be repeated as often as you wish.
You can produce the pair of Silks from some production apparatus then magically cause the Silks to change colors.
This is a variation of the classic Tarbell Color Changing Silks, with two silks changing together. Large 14″ silks, visible on a big stage for a large audience.
Colors indicated are for example only – the actual colors of the silks may vary in different sets.