Sit the person at a table or place a tray on their lap that they can work from.
Place the blank card on their working space.
Get the person to choose which object they want behind the flower pot.
Place the pieces next to the blank card with the colored side face up.
Hold up the sample with the chosen object in a position where you can see when their pupils focus on the sample.
Pay attention to the number of times they glance at the sample.