Quarks are said to be point particles, that is the have no volume like ..a point, string thoery says these point particles are actually not particles at all but vibrating open or closed end strings
The groups of particles are Bosons (force carrying particles of spin 0,1,2...), Fermions (matter constituents of spin 1/2,3/2,5/2..)But there are leptons like electrons and then there are quarks in the fermions group.Of which everything comes from e.g a proton is two up quarks and one down quark, sss, udd, etc etc
Note, these always combine to have no colour to be stable, although not in the every day sense of colour as light of visible wavelength is far too big