[opportune]

Is it true that the quarks themselves, in isolation, have that charge? Or is it that combining quarks into a baryon or meson gives the resultant particle a charge according to a fixed ratio of the constituent quarks?

Gemini advanced says it’s the latter, because of color confinement. But I’d defer to a human expert

[lnauta]

Quarks can not be alone, because of this confinement. What we see experimentally is that when we add energy to particles at some point they split into new particles and we never see a naked quarks.

We explain this by saying the quarks have a color charge and it must always be neutral. A single quark would be lets say red, but that's for some reason not possible. If we try to rip the quark out, it takes so much energy that this energy can be used to create another quark that results in a color neutral particle (red, antired)=meson, (red,green,blue)=baryon.

NB: this is a bit simplistic and other comments explain this quite in detail NB2: this color charge is just a name, its not an actual color