Ask your students what color they think light is. A silly question? Sunlight or light from a lamp may look "white" but it is really made up of different colors. Red, blue, and green are the primary colors of light. That means you can make any color from combinations of these three. We see an object in a certain color because that color is reflected by the object, while other colors are absorbed.
3 big flashlights
pieces of red, blue, and green cellophane paper
30 cm white card
white toy or ornament
1. Tape one piece of cellophane over the bulb end of each flashlight.
2. In a dark room, turn on the flashlights.
3. Shine the red and green flashlights on to the white card. What happens? (You make the color yellow.) Try mixing the blue and green lights. (You get cyan.) Now mix the blue and red lights. (You get magenta.)
4. Put the white toy in the center of the card and shine the three flashlights on it. Have the students circle around the toy to see it in different colors.
5. Ask them what color you will get if you shine all three lights on the white card at the same time. (You get white. White light is made up of red, blue, and green. These are called the primary colors. To get black, you would have mixed colored paints, not lights.)