Quarks changing colors is a fundamental property of the strong interaction, which is described by the theory of Quantum Chromodynamics (QCD). In QCD, quarks interact through the exchange of gluons, which are the force-carrying particles of the strong force. The strong force is responsible for binding quarks together to form composite particles such as protons and neutrons.
In QCD, quarks possess a property known as "color charge." However, it's important to note that the term "color" here is an analogy and does not refer to the colors we perceive visually. Instead, color charge is a property similar to electric charge in the electromagnetic interaction.
The key aspect of the strong force is that it exhibits a property called "color confinement." This means that individual quarks are never observed in isolation but are always found in composite particles or bound states called hadrons. These hadrons, such as protons and neutrons, are color-neutral.
The reason quarks change colors is related to the dynamics of the strong force. Quarks interact by exchanging gluons, which carry color charge. The exchange of gluons leads to a continual exchange of color charge between quarks, causing them to change colors. This process is a consequence of the fundamental principles and symmetries of QCD.
If quarks were to keep one color charge and not change, it would violate the principles of color confinement. In order to form color-neutral bound states like baryons (which are made up of three quarks), the quarks must have different color charges that continually interchange through the exchange of gluons. This ensures that the overall color charge of the baryon is neutral.
In summary, the continual exchange of gluons and the changing of color charges by quarks is a fundamental property of the strong force, necessary for the formation of color-neutral bound states and the maintenance of color confinement in QCD.