Magician displays a board with 3 colored light bulbs and 3 on/off switches.
Each colored switch operates the corresponding colored light.
Now the colored caps are removed from the switches are rearranged. Still they light their corresponding colored light.
You change the light bulb caps and still the switch of the same color operates it's correct light.
Finally, the board is placed on the table, facing down. You ask spectator to name any color, then turn over the board, the named color LIGHT is ON!!