Here's another color challenge for you: if we use a wide strip of paper instead of a pencil, we get many more colors. How are these produced? Think back to the other videos for a hint.
More Things to Try
Find out what happens when you use different colored paper for the screen. Try yellow, green, blue, red, purple, and so on.
If you let light from the three bulbs shine through a hole in a card that is held an appropriate distance from the screen, you will see three separate patches of colored light on the screen, one from each lamp. (Make the hole large enough to get a patch of color you can really see.) If you move the card closer to the screen, the patches of light will eventually overlap and you will see the mixtures of each pair of colors.