If you’re like most people, you probably haven’t spent much time wondering about how the multiple colors on a TV or a coffee table book are created. You may be surprised to learn that different mediums require diverse processes for color creation. These diverse processes of color creation are based on different color models, which all produce their own unique range of colors. Such ranges of colors are referred to as color spaces.
The RGB color model is the color representation method that’s used to create the colors you see on TV and computer screens. Here’s some more information on how this color model works.
What Is the RGB Color Model?
When you’re playing a game on your phone, browsing the internet on your computer, or watching your favorite series on TV, you’re seeing the RGB color model at work. This model is based on the three primary colors of light: red, green, and blue. As you’ve probably noted, the name of this model consists of the initials of these three colors.
There are two basic types of color models: additive and subtractive. The RGB color model is an additive one. In additive color models, light is used to display colors. This is why the RGB color model is primarily used for light-based devices, such as digital cameras and TVs. Although the same color model is used across digital devices, it is interesting to note that the colors that you see on different devices will vary. This means that the absolute red on a Galaxy phone may differ from that on an iPhone.
With additive color models, as colors of light are added, the color that you see becomes lighter. Interestingly, when all three primary colors are shown at the same time and at full intensity, the result is white. Conversely, when the three colors are superimposed with the least intensity, you’ll see black. In other words, black is the result of the absence of light.
How Does the RGB Color Model Work?
With the RGB model, an array of different colors is produced by mixing the three primary colors together at different intensities. Each color is represented by a triplet of values, called the RGB triplet, where each value describes the intensity of a primary color. The intensity of each color beam, which is called a component, can range from fully on to fully off.
When a component has the strongest intensity, the resulting color is a hue of that primary color. Conversely, when two components both have the strongest intensity, the resulting color is a hue of the secondary color formed by mixing these two primary colors. For instance, when red and green have the strongest intensity in an RGB triplet, you’ll see a yellowish color on the screen. Or, when blue and red are the dominant color beams, you’ll see a hue of magenta.
The intensity level of a color beam can be expressed in various ways:
Percentages
The value of a component can be expressed as a percentage, which obviously ranges from 0% to 100%. Here are a few examples:
| COLOR | RGB TRIPLET |
| Red | (100%, 0%, 0%) |
| Yellow | (100%, 100%, 0%) |
| Gray | (50%, 50%, 50%) |
| Green | (0%, 100%, 0%) |
Floating Point Numbers
RGB triplet values can also be quantified by dividing percentages by 100, leaving you with the corresponding floating-point numbers between 0 and 1. This type of representation is often used in theoretical analysis. Here are some examples:
| COLOR | RGB TRIPLET |
| Red | (1.0, 0.0, 0.0) |
| Yellow | (1.0, 1.0, 0.0) |
| Gray | (0.5, 0.5, 0.5) |
| Green | (0.0, 1.0, 0.0) |
Unsigned Integer Numbers
On computers, RGB triplets commonly consist of unsigned, 8-bit integer values that range from 0 to 255. These values can be written as either decimal or hexadecimal numbers. Here are examples of both:
| COLOR | RGB TRIPLET (DECIMAL) |
| Red | (255, 0, 0) |
| Yellow | (255, 255, 0) |
| Gray | (128, 128, 128) |
| Green | (0, 255, 0) |
| COLOR | RGB TRIPLET (HEXADECIMAL) |
| Red | #FF0000 |
| Yellow | #FFFF00 |
| Gray | #808080 |
| Green | #00FF00 |
How Does the Human Eye Perceive Colors?
Since the RGB color model is based on how the human eye perceives color, it may be useful to quickly recap on how exactly this process works. What makes yellow look yellow or red look red? Well, the human eye and brain work together to translate light into color.
Inside the human eye are special receptors, which are called “cones.” Although the human eye contains about six to seven million cones, there are only three types of cone-shaped cells. Each of the three types of cells is sensitive to specific wavelengths of light:
| WAVELENGTH | COLOR |
| Long wavelength | Redder light |
| Medium wavelength | Greener light |
| Short wavelength | Bluer light |
A long wavelength of light from the red end of the spectrum, for instance, will activate the cone cells that are sensitive to red light. They then respond by sending a signal through the optic nerve all the way to the visual cortex of the brain. The magnitude of this signal will depend on the number of activated cones and their signal strength.
Although humans only have three types of cone cells, which pick up wavelengths of the three primary colors, the brain is able to blend the signals from the three color receptors. In this way, you’re able to see a multitude of colors. For instance, when you look at a lemon in daylight, both the red and green cone cells are activated. After the brain has processed the signals from both receptors, you are able to see the yellow color of the lemon.
The color you see on a TV works the same way. If you zoom in on a digital screen, you’ll see many tiny rectangles, called pixels, which are made up of red, green, and blue regions. To display yellow on a screen, for instance, only the red and green regions of the relevant pixels are activated.
Alternatives to the RGB Model
Apart from the RGB model, there are many other color models, which all produce color in different ways. Here is a short overview of a few of these alternative color models:
The CMYK Color Model
As opposed to the RGB model, which is an additive color model, the CMYK model is a subtractive one. While an additive color model works with light, a subtractive color model works by subtracting light. With a subtractive model, certain wavelengths are removed from white light by using a filter. For instance, with a green filter, red is subtracted, while a yellow filter subtracts the blue parts of the spectrum.
The CMYK model employs the basic material colors, which are cyan, magenta, and yellow. The “K” stands for black ink, which is added to create a deep and neutral black. The CMYK model is used for color printing. The process entails using colored ink to mask colors on a white background, in this way subtracting brightness from the white background.
The HSL Color Model
The HSL color model is identical to the RGB model, except for one difference: the way that the colors are expressed. Similar to the RGB model, the HSL model presents colors as a combination of red, green, and blue, and it is also an additive color model.
Where the HSL model differs from the RGB color model, however, is that it also accounts for hue, saturation, and lightness. The hue of a color refers to its position on the color wheel, which is represented by degrees. Saturation refers to the vividness of a color, which is expressed as a percentage. Lastly, lightness is also expressed as a percentage, with 0% representing black and 100% representing white.
As such, the HSL color model is a more sophisticated and intuitive system. Instead of presenting colors as a combination of different wavelengths of light, the HSL color model expresses colors as a fraction of the entire color spectrum.
The CIE Color Model
The CIE color model uses a combination of three color values that closely resembles red, green, and blue. These values, which are referred to as tristimulus values, are then plotted onto a 3D space, and when combined, can accurately reproduce every single color that the human eye can perceive. For this reason, the CIE color model is regarded as the most accurate color model.
As opposed to any other existing color model, the CIE color model takes into account the chromatic response of the eye, which is the function that’s responsible for the stable appearance of the colors of objects, despite the wide variation of light that may be reflected from an object.
The RYB Color Model
Like the CMYK color model, the RYB color model is a subtractive color model. However, in this model, red, yellow, and blue pigments are considered the primary colors. This color model is often used in art and design education, particularly painting.
Artists typically use the RYB color model since they work with red, yellow, and blue primaries. Printers, as mentioned above, use modern subtractive color methods based on cyan, magenta, and yellow primaries. This means that the RYB color model is an older color system that predates modern scientific color theory.
