First off, what are colors?
We can’t talk about colors unless we first establish what they actually represent. With that in mind, I’d like you to think about how we see the things around us. Our eyes can only perceive objects in the presence of light: it reflects the light and a slightly deformed image of the object is formed on our retina. But the question still remains: what are colors?
Considering how much we depend on light to be aware of objects that surround us, we could put it short and say that, as far as Newton's demonstration goes, color is a quality of light.
Now that we know what colors are, how do we perceive them?
Light is a form of electromagnetic radiation, which is why it shares the same properties as both waves and particles. That's why different beams of light will have different frequencies, wavelengths, and energies; you could think of them as rivers, with a variety of paces, lengths, and widths. To understand the notions better, I'll provide some definitions:
Frequency represents the number of waves passing a fixed point in space in a unit of time and is expressed in units of hertz.
Wavelength represents the distance between two corresponding points of consecutive waves, often expressed in units of meters.
As for the energy of a beam of light, it's easily compared to that of a small particle moving at the speed of light. To express the smallest quantity of light of any given wavelength, we use the term "photon". Usually, the energy of a photon is expressed in units of electron volts.
With that in mind, we can move on and state that light is the only form of electromagnetic radiation that our eyes can perceive, through colors. Each color corresponds to a different wavelength, ranging from 400 nm (nanometres) for the color violet to 700 nm (nanometres) for the color red. This is why we say that the visible light is located exactly between ultraviolet and infrared radiations.
Are colors actually real?
SPOILER ALERT: No! Colors do not actually exist.
Color is created by our brains, to understand the image of an object. One of the most important properties of light is reflection. It allows it to return after striking the surface of certain objects. Light waves often move at the speed of light, and, until they come into contact with a reflective surface, they travel in straight lines. The radiations have a tendency to reflect themselves naturally after striking the surface of a reflecting material. Some examples of objects that reflect light are mirrors, eyes, metals, the surface of water, etc. But not every object reflects light! Certain objects absorb light instead. For example, an apple absorbs all colors except green, and since green is reflected, we see it. Another example is when all of the light is absorbed and we see black, or when all of the light is reflected and we see white. That's actually why you shouldn't wear black clothes in summer: they absorb more heat.
In conclusion, colors are what our brains perceive different wavelengths as. I hope next time you eat an apple you'll remember that the only reason it looks so tasty is because of the values of the light's wavelengths, and not because of a magical fertilizer!
Bibliography:
https://www.britannica.com/science/color/The-visible-spectrum “Color-The visible spectrum”- Kurt Nassau
“Examples of Objects That Reflect Light”
“What is Color?” https://res.cloudinary.com/rs-designspark-live/image/upload/c_limit,w_829/f_auto/v1/article/Visible-Spectrum_aeaf1fbca58d48b17b5ee565af16a9268021cdb6
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