The tools we use to describe color are different when the color is printed than from when it is projected. Projected color is additive. Printed color is subtractive.
Visible light is a small part of the electromagnetic spectrum, between the wavelengths of 400 and 700 nm (nanometers = billionth of a meter). In 1666 Sir Isaac Newton used a glass prism to refract white light at different angles according to wave length. He saw a rainbow of colors, which he passed through a second prism to re-form white light. He concluded that white light is a mixture of all the colors of the visible spectrum.
||Sir Newton was playing with additive color. No light (or color) is black. All light (all colors) is white.|
Each color of the spectrum has a specific frequency. Adding different colors of light together increases the number of frequencies present and the more colors you add the closer it becomes to white. Therefore, light is called an additive color mixing system. This type of color mixing is used in computer monitors, TV sets, and to illuminate actors on stage.
The color we see on paper is created using a subtractive model, where the frequencies that are not absorbed form the color we see.
When you project light, you are sending out frequencies of light that add together to form a certain color beam. Think of it as painting with light. In contrast, the color we put down on paper works exactly the opposite. The color we we see is the spectrum of light which is reflected by the paper or by the ink, crayon, or marker we put on the paper.
Historically artists and designers have not worked with light but with paints and pigments. Colors of paint absorb most of the light frequencies and reflect back only the wavelength that defines the color you see. Mixing different paints makes a darker color because more of the light frequencies are absorbed. This method of mixing colors is called subtractive because each color absorbs, light frequencies, subtracting them from the total mixture.
||A subtractive color model is the very first type of color we learn as a child, when we are taught that the three primary colors of red, yellow, and blue can be mixed to form all colors. The printing inks magenta, yellow, and cyan are essentially a more sophisticated version of our childhood crayons.|