Can RGB make all colors? Exploring the Limitations of RGB

Red, Green, and Blue. These three colors define the so-called RGB color model. They are the primary colors of light, and their combination can create a wide range of colors. However, can RGB make all colors? Well, the simple answer to this question is no. But we know that you will not be satisfied with a two-letter answer. So, in this article, we will explain to you the reasons why the RGB color model has limitations, and the following topics:

• What is the RGB color model​?
• Can RGB make all colors?
• Numeric representation for the RGB color​ model.
• Are RGB primary colors​?
• Are there 16,777,216 colors​?
• What colors can't humans see​?
• And much more.

So, pick up your three primary colors and let us show you how to make Magenta or Cyan colors.

RGB is an acronym for Red, Green, and Blue, and it is known as an additive color​ model. In the RGB model, these three primary colors are combined in various ways to create a wide range of colors.

The science behind this additive color model is based on the superposition of light beams corresponding to the primary colors. Each beam has a specific frequency, and the combined light spectra produce a distinct color that we see with our eyes. The ability to perceive color using the RGB model is known as trichromatic color vision, a theory formulated by Thomas Young and Hermann von Helmholtz, that explains how the human eye has three independent channels for conveying color information.

The RGB color model is applied to various devices, including TVs, video cameras, image scanners, and digital cameras. Moreover, the additive features of RGB contrast with subtractive color models, such as the CMY (Cyan, Magenta, and Yellow) model. The CMY color model is typically applied to paints, inks, color printers, and dyes, as the resultant color depends on the specific frequencies of light reflected by them when viewed.

Now that you are familiar with some concepts about the RGB color model, let us demonstrate its limitations in generating colors. The RGB model can make a large number of colors. The total number will depend on the number of bits per channel and is computed using the formula:

where:

• $\mathrm{N}$ — total number of colors; and
• $\mathrm{bpc}$ — number of bits per channel.

In the table below, you can verify the number of different sets of bits using the RGB color model:

The standard RGB model (or sRGB) is the one that has 8 bits per channel. As we pointed out, it can generate precisely 16,777,216 colors, which can be represented as a surface in a graphic called a chromaticity diagram. In the figure below, you can see the chromaticity diagram together with the standard model, which describes the human color vision, named CIE 1931:

As we can see in the previous graphics, the sRGB Color fills only part of the human color vision. Moreover, the point highlighted as $\rm D65$ represents the white color in the RGB color space.

Therefore, we can realize that despite being able to create 16,777,216 colors with the standard RGB color model, we are unable to reproduce the different colors observed in the gray region of the chromaticity diagram.

Now that you know the answer to the question: "Can RGB make all colors?", let's see how to represent the RGB triplet. There are several ways to quantify the different colors that you can create using the RGB color model. The most popular forms are presented in the table below:

Each one of these triplets unveils how much red, green, and blue are present in each specific color. Moreover, it is important to point out that the different components of the triplets can vary from 0 to the maximum value of the respective representation.