Color has three distinct properties:
Hue – spectral color name
Value – lightness or darkness
Saturation – brightness or dullness
Although you see color in our brain, it is the eye that has the receptors that tell your brain what you are looking at. There are two sets of receptors in the retina in the back of the eye: rods and cones.
There are about 125 million rods (named for their shape). They are very sensitive to light but are mostly color blind. We use them in dim light and so the saying: “all cats are gray in the dark.”
The color detectors in the eye are the cones. There are about 7 million of these in three forms concentrated in the center of vision. Individual cones can only sense one of three narrowly defined frequencies of light: red, green and blue. The response from these three “primary” colors is sorted in our brain to give us the perception of color. One or more of these color receptors malfunctions in a color blind person.
Color is a property of light. Our eyes see only a small part of the electromagnetic spectrum. Visible light is made up of the wavelengths of light between infrared and ultraviolet radiation (between 400 and 700 nanometers). These frequencies, taken together, make up white (sun) light.
White light can be divided into it’s component parts by passing it through a prism. The light is separated by wavelength and a spectrum is formed. Sir Isaac Newton was the first to discover this phenomenon in the seventeenth century and he named the colors of the spectrum.
If the ends of the spectrum are bent around and joined a color circle (color wheel) is formed with purple at the meeting place.
Color has three distinct properties: hue, value and saturation. To understand color you must understand how these three properties relate to each other.
The traditional color name of a specific wavelength of light is a hue. Another description is: spectral color. All of the colors of the spectrum are hues. There are only limited hue names: red, orange, yellow, green, blue and violet. Magenta and cyan are also hues.
Value is concerned with the light and dark properties of color. All colors exhibit these properties. The hues have a natural value where they look the purest. Some colors, like yellow, are naturally light. Some, like violet, are darker.
All hues can be made in all values. Adding white paint will make any pigment lighter. Adding black paint will make most pigments darker, but will cause yellow paint to shift in hue to green.
Value can exist without hue (see achromatic). Black, white and gray are values without color.
Saturation is concerned with the intensity, or the brightness and dullness of color. A saturated color is high in intensity — it is bright. A color that is dull is unsaturated or low in intensity. Another term for saturation is chroma. A color without any brightness (no hue) is achromatic (black, white and/or gray.
There are two theories that explain how colors work and interact. The light, or additive theory deals with radiated and filtered light. The pigment, or subtractive theory deals with how white light is absorbed and reflected off of colored surfaces. This course will investigate the pigment theory.
Light theory starts with black — the absence of light. When all of the frequencies of visible light are radiated together the result is white (sun) light. The color interaction is diagramed using a color wheel with red, green and blue as primary colors. Primary here means starting colors. These are the three colors that the cones in the eye sense. This is an RGB color system (Red, Green and Blue).
The primary colors mix to make secondary colors: red and green make yellow, red and blue make magenta and green and blue make cyan. All three together add up tomake white light. That is why the theory is called additive.
You can see an example of light theory in action almost every day on a computer monitor or a colored television. The same three primary colors are used and mixed by the eye to produce the range of colors you see on the screen.
Pigments behave almost the opposite of light. With pigments a black surface absorbs most of the light, making it look black. A white surface reflects most of the (white) light making it look white. A colored pigment, green for instance, absorbs most of the frequencies of light that are not green, reflecting only the green light frequency. Because all colors other than the pigment colors are absorbed, this is also called the subtractive color theory.
If most of the green light (and only the green light) is reflected the green will be bright. If only a little is reflected along with some of the other colors the green will be dull. A light color results from lots of white light and only a little color reflected. A dark color is the result of very little light and color reflected.
The primary colors in the pigment theory have varied throughout the centuries but now cyan, magenta and yellow are increasingly being used. These are the primary colors of ink, along with black, that are used in the printing industry. This is a CMYK color system (Cyan, Magenta, Yellow and (K)black). These are the secondary colors of the light theory.