Particle operators for the description of a system of families of particles of different kind are introduced. The generalized commutators and Klein transformations are discussed in some detail. The color description of parastatistics is given.
Possible generalizations of the statistics of identical particles, parastatistics, and the corresponding theories of parafields are reviewed. The connection between parastatistics and cases of degeneracy of particles with respect to an internal degree of freedom is discussed, and also the restrictions that are imposed on internal symmetries if they are given a parafield description. In particular, the difference between the hypotheses of ''three-color'' quarks and ''paraquarks'' is discussed.