A Prism can be used to break apart white light into its component colors. This shows that white light is a mixture of the projected colors.

Although the spectrum shows that white light contains a continuous range of colors, colors from just three areas of the spectrum could be mixed to form any other color including white. These three colors of light are from the red, green, and blue parts of the spectrum.

Color is also a physiological manifestation of the Human Eye. When the image of the apple's red skin is focused at the back of the eye, it effects red sensitive receptors to a greater extent. The color is then perceived as being red. There are also color receptors (cones) that are particularly sensitive to the other primary colors of light. All other colors effect these receptors to varying degrees so that we are able to discern a great range of various color mixtures.

When the three primary colors of light are mixed, the intensities of the colored light is being added. This can be seen where the primary color illumination overlaps. The yellow formed when red light is added to green light is equal to the illumination of the red and green combined.

Likewise the cyan formed by adding green and blue light is brighter than its components. The same goes for the magenta and its red and blue components. The mixing of colored light is called additive color mixing. White light is perceived where all three additive primaries overlap. Since the white mixture results from the adding of three color light sources, the white light appears to be the brightest of all. By varying the intensities of the individual light sources, a full range of colors can be obtained. Television screens and PC monitors use an additive color process.

Color TV

The primary colors for mixing paints, inks, and dyes, are not the same as for mixing light. The red, blue, green of light mixing adds colors to make new hues. The magenta, cyan, and yellow of mixing pigments and dyes subtracts colors to create new hues. This is referred to as subtractive color mixing. The dyes of inks absorb certain colors. Any color that is not absorbed (subtracted) is the hue that we see. These dyes act as filters that subtract one or more colors. By varying the proportion of the colors in a mixture, a full range of colors can be produced.

In this diagram, filters are used to represent the color dyes. Here, we do not have multiple light sources overlapping to form new colors as shown for mixing colored light. Instead, the light from a single source enters the yellow filter, and blue is absorbed (subtracted out). Red and green are not absorbed by the yellow filter and continue through it. The magenta filter then absorbs the green. Whatever color emerges from the filters is the hue created from the mix. In this case we should see red showing through.

Sometimes we may hear of other colors used for color mixing besides those mentioned above. However, the red, blue, green and the cyan, magenta, and yellow systems of color mixing can create the greatest range of color from only three initial colors. Black and/or white may also be used in some types of subtractive color mixing. An artist can use whatever colors are needed to create a painting. It would be after all a work of art and not tied to the requirements of printing, or photography. Also, using ready made artist colors saves time, and allows for uniformity over large areas. The same goes for stage lighting. A bank of red, green, and blue stage lights and dimmers could be used to create any possible color illumination. This would be a scientific approach, but there is no necessity for this in a theatrical setting.

Additive

Subtractive

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