No, protons cannot be seen by human eyes. The reason for this is that the wavelength of visible light, which is the range of electromagnetic radiation that our eyes can detect, is much larger than the size of a proton.
Visible light has wavelengths between approximately 400 to 700 nanometers (nm), while the size of a proton is on the order of femtometers (10^-15 meters). The scale difference between the two is enormous. As a result, the interactions between visible light and protons occur on a scale that is far beyond the resolution capabilities of our eyes.
To see an object, our eyes rely on light reflecting off or being emitted by that object and entering our eyes. The photons of visible light interact with the atoms and molecules in the object, and these interactions give rise to the perception of the object's color and shape. Since the size of a proton is much smaller than the wavelength of visible light, there is no significant interaction between individual protons and visible light.
However, it is worth noting that there are scientific techniques that allow us to indirectly observe and study protons. For example, high-energy physics experiments and particle accelerators can provide information about the behavior and properties of subatomic particles, including protons. These methods rely on detecting the effects of particle interactions and analyzing the resulting data using specialized equipment and techniques.