For a school play, Mandy has been given a budget within which she has to accommodate all the expenses. The play has a scene where the main character meets a fairy one day. For the scene, Mandy needs a yellow light to fall over the character but her budget does not allow her to rent a color gel, so she uses Sebastiano Serlio’s technique of creating colorful lights. What do you think Mandy must have used to create a yellow light?