Take the prism from the fancy red box and place it vertically on the table.
Shine the flashlight on the prism and see if you can make the rainbow colors.
Use the paper slit to make the light beam narrower - should be much better
Take the 3 flashlights from the yellow box, and combine R, G, B to make different colors. Can you make white?
From the big case, take the 5-beam laser box and the power supply.
Explore how light is refracted by the different components.
Can you place multiple components and make 2 beams come together on the screen?
How about 3, or 5?