All four gauge transformations of the fermion Lagrangian
  Four global gauge transformation of the free fermion Lagrangian is considered. One of these transformations has S(1) symmetry, other transformation has SU(2) symmetry, and two others have SU(3) symmetry. It is supposed, that these transformations determine four grades of the physics interactions - electromagnetic, weak, gravitational and chromatic. 
Gunn A. Quznetsov