It depends what you mean by this. That part of the electromagnetic spectrum that we perceive as color is, yes, a very narrow part.
And, say, we perceive the infrared part of the spectrum as heat, not as color.
However , in order to assert that the color spectrum is more diverse, you need to understand - it is more diverse for whom. If we look at a certain natural object, then it has a certain color just for us. For another biological species, it can be either this color or another, depending on the characteristics of the vision device. But there is no "true color" of an object that we could see, but do not see due to the limitations of our vision, because the "true" color for us, as humanity, is the color of the object that is perceived by a healthy person .
The color of, for example, a transparent object depends on, roughly speaking, which atoms in its structure passed which part of the light passing through it, which absorbed (not counting more complex optical effects). We know what the spectral curve of the light of our Sun is, we can measure the spectral curve of the light that passed through the transparent object.
And then, not seeing the object, but seeing the spectral curve of transmission / absorption, knowing the sensitivity peaks of the detectors "in our eye, we can, plus or minus, guess what color our brain will perceive, ie. what color this transparent object will be for the observer.
At the same time, due to the combination of the eye device and the work of the brain, the subjective perception of color in a particular person will be slightly different. It is even quite a trainable quality. For example, as a gemologist, it is important for me to distinguish between many different yellow stones or red and so on. Because it's money =) The value depends on the color.
This means that two yellow objects that are the same yellow for another person will be different yellow for me. And some color will be orange-red, not just red, five blue stones will be differently blue, and so on. Can this be called the fact that I see colors more varied? Yes and no, because it is still within the same spectral range available to us.
It can be more difficult. People with four "detectors" in the retina also do not begin to perceive X-rays as a color :) But due to the fact that objects in the real world are not illuminated by light of only one wavelength and often have a color as a combination of some colors, for adding a new "detector" with a new peak of sensitivity, conventionally, what we see as a shade of pink (which itself is not a spectral color), a person will see as a shade of violet or in whatever part of the spectrum a new peak of sensitivity appears. There will be not so much more colors as more mishmash from the point of view of a person with three detectors. Conventionally, for a normal person there will be a uniformly brown object, and this person will also see a violet spot there.
There have been experiments in the USA and China to increase the perception of a part of the infrared range by the eye and the brain, and thisexcellent for night vision, but during the day it would turn out that warm objects mix with their color the same color as infrared would be perceived. Perhaps a special red. And now a man looks at his warm hand, and the skin is not beige, but spotted and red :)
Again, does this mean that the skin is "really" just like that? No, it means that it would be perceived that way, and if everyone would see it this way, then it would already be considered that the skin is just that.
Therefore, everything is relative :)
The fact that all colors are decomposed into three components - red, slit and blue - is the peculiarity of our vision, and not some physical property. In reality, there is, for example, spectral orange, which is not a mixture of red and green (something like the FF8000 for displaying orange on a monitor). If we had more different sensors tuned to different wavelengths, then even the same area from 400 to 780 nanometers, we would perceive in more detail and interestingly, distinguishing more colors and shades.
Recently on different resources wrote about the artist Conchetta Antico with a genetic anomaly - tetrachromatism. Adding a fourth sensor allows it to distinguish 100 times more colors.
True, you need to clarify: does not see, but perceives. The difference is that the eye really sees a continuous spectrum, but the brain distinguishes between individual colors and shades. We are accustomed to seeing seven primary colors in a rainbow, in the Middle Ages only three were distinguished, and more or less accurate color reproduction begins with 65 thousand shades. In the same way that the spectrum of sound vibrations is continuous, and even the most trained hearing can distinguish notes.
This ability is largely determined by the physiological characteristics of the nervous system, which are collectively called the ability to fine differentiation.
Recently there was a question about how the "color depth" affects the quality of the picture thequestion.ru Nobody gave an answer there, but in fact, not everyone will see the difference between HighColor (16-bit) and TrueColor (32-bit) ... This is the most obvious example of how the brain can distinguish colors in different ways.
Indeed, a person does not see the entire light range, only light with a wavelength of 400 to 780 nm. This is our red to purple rainbow. But other living beings can perceive radiation outside this range. So, it is known for certain that insects see ultraviolet radiation (it is in the color range outside our violet), and those flowers that are white for us may have a color and even a pattern for them. Birds also see ultraviolet light. The snake perceives infrared rays. They distinguish warm-blooded animals by them while hunting.
In addition, I will say that light radiation belongs to the category of electromagnetic radiation, and its spectrum in the universe is extremely huge, and a person perceives a very small part of it.