THE PRIMARY COLORS OF LIGHT

Light has its own set of three primary colors. These are the "additive" primary colors.

The primary colors of light are red, green and blue. They should not be confused with the three primary colors used for paints, inks, dyes and other colorants. The primary colors for light combine in a different way.

Mixing color light is called additive color mixing, because adding light from two or more sources produces the mixed color. The illumination from two or more colored light sources when added together will give more illumination than any of the lights by themselves.

This can be seen where the color illumination overlaps. The yellow formed when red light overlaps green light will be brighter than either the red light or green light alone.

When the right amounts of red, green and blue light come together, the result appears as "white" light.

One of the most common uses of mixing the primary colors of light is for  televisions, tablets, smart phones and computer monitor screens.

These types of screens are made up of rows and rows of red, green and blue stripes. From normal viewing distances, the stripes are usually not noticeable. The human eye causes these stripes that make up a screen image appear to blend together. Since they blend together in this way, the stripes act just as if they are mixing the colors of light together.

	The changing intensity of each stripe segment allows for all the colors and shades of a digital image or a television scene to be displayed on the viewing screen. If we view a screen image with a powerful magnifying glass, we would see the ever changing brightness of red, green and blue pixels that make up the moving image.
	Older CRT screens used three electron beams that raced across the screen, "painting" images dot by dot. Behind the viewing screen was a special metal mask with thousands of holes. This mask separated the angles of the beams so that each beam could only hit either red blue or green dots. This was truly an ingenious technology for its time.	Animated breakaway representation of Cathode Ray Color Tube
Each tiny dot printed inside the screen was made of phosphor chemicals that glow for only a split second when hit by an electron beam. This happens so fast that it looks as if the screen image is appearing continuously. The composition of the three different phosphor dots enables each dot to glow either red green or blue depending on its chemical makeup.

These technologies use the red blue and green primary colors of light. What is interesting is that there is a relationship between the three primary colors of light and the three primary colors of paints, inks, dyes and other colorants. Since this website is about both additive and subtractive color mixing, the following chart shows this relationship.

ANY TWO ADDITIVE PRIMARY COLORS MIX TO MAKE ONE OF THE SUBTRACTIVE PRIMARY COLORS 

For more about the "subtractive" primary colors, select the topic "Subtractive Color" from the tabs on the top of this page.