Colors 101

Light can be every color imaginable. When several light beams of different colors combine, they mix to form a ray with a new color. There are seven basic colors: red , orange , yellow , green , blue , indigo , and violet . Other colors are mixtures of the basic colors, and can be separated into their components with special tools.

Different combinations can be used to create the same color. Even some of the basic colors can be created as a mixture of other colors. For example, when you see yellow  on your smartphone screen, you're looking at a mixture of green  and red  lights:  . So sometimes, without special tools, it is hard to say what we’re seeing—one pure color of light or a mixture. In fact, any color can be obtained by mixing just three primary colors: red , green , and blue .

You may have noticed that white is not in this list of basic colors. A beam of white light is always a mixture of several colored light beams. By removing some of these beams, we can create new colors. The colored cards from the set are called optical filters . They absorb the rays of particular colors, letting the rest through. The cyan filter  absorbs the red part  of white light, the yellow filter  absorbs the blue part , and the magenta filter  absorbs the green part . The penlight generates white light, and if you place a filter in front of it, only some of the colored beams can pass through. You see the mixture of remaining colors on the screen. The second filter blocks some more colors, and the final color changes. If the filters block all the colored beams, no light will reach the screen.