Trying to calculate the number of colors has been a fascination for mathematicians, physicians and artists for centuries. While the simplest answer to the above question would be ‘infinite’, the subject is a lot more complicated than that. Does color really exist or is it just a perception? If it is only a perception, can all of us distinguish a similar number of colors? Do culture and language play a role in the perception of color? Is color subjective?
Simply put, colors don’t really exist because they are perceptions. Color is not inherent in objects; it is actually light that is reflected or absorbed by objects and the manner in which the human brain perceives this light. In scientific terms, color is the range of light in the visible spectrum that the human eye can see.
Colors are perceived and processed by the human eye through a physical process: Light rays contain color and they consist of electromagnetic waves spreading from any source. When these rays touch an object, the object reflects or emits some of the rays. This electromagnetic radiation stimulates the photoreceptor cells in the eyes and the light that the object reflects is in turn perceived (seen) as color. The reflection can be altered by the object’s own properties as well as the amount of light that exists in the setting.
What all this means is that color does not ‘exist’ in the real sense. If there is no light, then there would be no color. This is why scientists consider black as the absence of any color while artists see it as the darkest color.
While an infinite number of colors exist, color systems are designed to display a certain number of colors. So how many RGB colors exist? And how many hex colors are there? The answer to both of the questions is the same: 2563, which is 16,777,216.
This means that in RGB, all red, green and blue have 256 (8bit) values (shades) each. Therefore, RGB displays 256 x 256 x 256 = 16.777.216 colors.
As hex is simply a different kind of notation, the number of colors it displays is the same. In standard #RRGGBB notation, the same number of colors - 16.777.216- can be displayed. Meanwhile, this number is quite beyond the number of colors that the human eye and brain are able to differentiate.
While all light rays contain color, different colors have different wavelengths. The human eye is adept at seeing only light with wavelengths between 380 and 750 nanometers. This is called the visible spectrum. It begins with violet (wavelengths between 380 and 450 nm), shifts to blue, green, yellow, and orange, ending with red (between 590 and 750 nm).
Thus, the color with the longest wavelength that is visible to the human eye is red. The color with the shortest wavelength that the human eye can see is violet. The reason we cannot see ultraviolet is that its wavelength is even shorter than violet. Similarly, infrared cannot be seen by the human eye because its wavelength is longer than red itself.
Meanwhile, colors like pink, fuchsia or brown are not present in the visible spectrum. This is because they are the results of the human eye mixing different colored wavelengths.
In fact, the answer to this question varies from person to person. However, while color perception is subjective, the average human eye is thought to be able to distinguish at most a few million colours. There are also some scientists who put this number at around only a million.
Subjectivity vs. Objectivity: How to Specify Colors?
A study at University of Rochester has determined that individuals tend to perceive colors even when the number of cones in their retinas vary. However, when people are asked to match colors to samples, factors such as light source, noise, age, memory and mood may alter perception. What follows is that subjectivity of color perception makes it complicated to pin down, communicate and compare colors in a standard sample.
This is why more objective methods such as color coordinates and color models have been developed. By assigning numeric values to specific colors, the subjectivity aspect of color perception has been surpassed.