Background

There are two main types of color mixing: additive color mixing and subtractive color mixing. Additive color mixing is creating a new color by a process that adds one set of wavelengths to another set of wavelengths. Additive color mixing is what happens when lights of different wavelengths are mixed. When we add all of the different wavelengths of sunlight, we see white light rather than many individual colors. It is called additive because all of the wavelengths still reach our eyes. It is the combination of different wavelengths that creates the diversity of colors.

Most monitors, phones, and telelvisions use additive color mixing to create their range of colors. The illustration below shows how a monitor uses red, gree, and blue colors dots on the screen to create different colors. The photograph on the left shows the screen as it actually appeared with a small section at the intersection of the red, blue and green circles as indicated. Blowing up the image by taking a photograph really close to the screen, as shown in the photograph on the right, shows the individual color dots on the screen. In the upper right part of the screen, the red circle is made from where only red dots are on; the yellow portion of the image has both red and green dots turned on; the magenta region has red and blue dots turned on; finally, the white area has all three dots turned on.

Subtractive color mixing is creating a new color by the removal of wavelengths from a light with a broad spectrum of wavelengths. Subtractive color mixing occurs when we mix paints, dyes, or pigments. When we mix paints, both paints still absorb all of the wavelengths they did previously, so what we are left with is only the wavelengths that both paints reflect. It is called subtractive mixing because when the paints mix, wavelengths are deleted from what we see because each paint will absorb some wavelengths that the other paint reflects, thus leaving us with a lesser number of wavelengths remaining afterward. So the easy way to remember the difference between additive and subtractive color mixing is that additive color mixing is what happens when we mix lights of different colors whereas subtractive color mixing occurs when we mix paints or other colored material.

The photographs below illustrate subtractive color mixing using lights. The picture on the left shows the red, green, and blue lights sourses. Where they overlap the wall will look white in the picture on the right. Since the different light sources are in different positions, they shadows cast for each light source will be in a different position. The blue light source will cast the right shadow, the green source will cast the middle shadow, and the red light source will be on the left. Look closely at the shadows for the pinky of the hand. The shadow for the blue light is yellow because the blue is blocked. The shadow for the green light is magenta because the green is blocked. The shadow for the red light is cyan because the red is blocked.

Another way to see subtractive color is to look at light going through a filter, much like on theater lights. In the photograph below, you can see a white light that goes up to a magenta filter. After the light passes through, those wavelengths that do not contribute to the magenta color have bee subtracted or removed from the light to give the magenta color.

Use this activity to explore color mixing and its various properties.

Instructions

Full Screen Mode

To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.

Illustration Tab

Settings

Below is a list of the ways that you can alter the illustration. The settings include the following:

Screen Area: click on one of the primaries to move it around. Mixing only occurs where primary circles overlap.
Type: choose whether to explore additive or subtractive color mixing.
Primaries: Control the intensity of each of the primaries: Red, Green and Blue for additive, and Cyan, Magenta and Yellow for Subtractive.
Background: If you are doing subtractive color mixing, the you can only subtract wavelengths that are present. In this illustration, this is shown by the background color. Change the background color and see how that alters the colors you can create with subtractive color mixing.
Reset Positions: return the the primary circles to their original position.

Reset

Pressing this button restores the settings to their default values.

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