This activity shows two different ways you can mix colors together to form a new color.
The first way of mixing colors uses different colors of light. When we mix color this way, the more light we add, the brighter the combined color gets. By mixing just three colors of light, Red, Green and Blue, we can make any color we want. These are the primary colors we use to make the millions of different colors we see on TV and computer screens.
The other way to mix colors uses paint, inks, or dyes. The inks absorb different colors of light, subtracting it from what you see. The more ink you add, the more light is absorbed, and the darker the combined color gets. Just the opposite of mixing color with lights! Again, we can mix just three primary colors to make many new colors. The primary colors for paint/ink are Cyan (a special shade of blue), Magenta (a special shade of pink), and Yellow.
The two sets of primary colors are related. If any two colors from one group of primary colors are combined, they make a primary color from the other group. The primary colors of light are secondary colors for paint and ink; the primary colors of paint and ink are secondary colors in light.
Red light + Blue light = Magenta
Magenta paint + Yellow paint = Red
Blue light + Green light = Cyan
Yellow paint + Cyan paint = Green
Green light + Red light = Yellow
Cyan paint + Magenta paint = Blue
Why are these groups of colors called primary colors?
The three primary colors are the minimum number of colors that can be mixed to make the greatest number of other colors.
In each group, none of the primary colors can be made by mixing the other primary colors.
Here we have a picture of some flowers. The picture is actually made up of just the three primary colors for light: red, green and blue. Your eyes mix these three colors, so you see all the different shades of pink, yellow, cream and grey. If we separate the Red, Green and Blue components, they look like this:
Notice how the flowers that are red in the original picture look black in the Green and Blue images. That's because you can't make red by mixing green and blue light.
In our paint/ink mixing activity, you mix Cyan, Magenta and Yellow together and get black. When painters or printers mix those inks in real life, the colors don't mix together to make a perfect black. They just make a muddy brown, so you also need some pure Black paint or ink. If we wanted to print a high quality picture of the flowers using the separate ink parts, the four parts would look like this:
Here, you can notice how the yellow flowers stand out in the yellow image, and the red flowers stick out in the magenta image.
Color and the Human Eye
The back wall of your eye, or retina, is lined with light-sensitive cells that send information into your brain about what you're seeing. The two main types of cells in the retina are called rods and cones. Rods aren't color sensitive, but they help us see when there's not much light, like in a dark room or at night. Cones are color sensitive cells, but they need much more light to work. There are three different kinds of cones. Each kind senses a different color of light - you guessed it! The three colors are Red, Blue and Green!
This in-depth tutorial by Byron Canfield talks about how inks are used to make all kinds of colors, and explains the difference between light passing through transparent objects and reflecting off opaque surfaces.