Quarks
The model of an atom that most people know is a nucleus surrounded by an electron. The nucleus is made up of protons and neutrons. However, protons and neutrons are not fundamental and are made up of more particles, called quarks.
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Image from: https://en.wikipedia.org/wiki/Standard_Model
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Meson: A type of Hadron that contains a quark and antiquark bound together. They are color neutral.
Baryon: A type of Hadron that contains 3 quarks. They are also color neutral. (e.g., protons and neutrons)
Hadron: Particles that feel the strong nuclear force meaning they contain quarks.
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There are six flavors of quark: Up, down, charm, strange, top, and bottom. A proton has two up quarks and one down quark with electromagnetic charges +2/3, +2/3, and -1/3 to equal 1. A neutron has two down quarks and one up quark with electromagnetic charges -1/3, -1/3, and +2/3 to equal 0.
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Quarks carry the color charge. To explain this, we need to know about the Pauli Exclusion Principle. The Pauli Exclusion principle says that there can't be two fermions with the same state in the same quantum system. If we apply this law to a uuu baryon (a baryon with three up quarks), at first it would seem like the principle is violated. Each quark has the same charge, +2/3, and at least two of the quarks have to have the same spin (up or down). We need a property that can take on three different values, and that property is color.
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The particles do not actually have a color as seen in the macroworld. The term "color" is just a useful analogy for describing a scale with three values rather than the two for spin. The three charges for color are red, green, and blue. Just like how opposites charges attract and similar charges repel in the electromagnetic force, color wants to achieve a "white" neutral color. This is why we use those colors. By mixing red, green, and blue in optics, we get white.
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Then what about meson (A particle with two quarks and has neutral color)? This is fixed by the existence of antired, antiblue, and antigreen colors. A red quark and an antired quark would be in a Meson.
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Just like how the charge that we know is the charge for the electromagnetic force, color is the charge for the strong nuclear force. The strong nuclear force is one of the four fundamental forces of the universe, but we will get into that later.
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