Color gauge group and new low-energy phenomena

The unbroken color gauge group SU(3${)}_{\mathit{c}}$ may arise as a consequence of the spontaneous symmetry breaking of some larger group. The possible uniqueness of the color gauge group is examined under a set of minimal assumptions. Under these assumptions it is shown that the color groups ${\mathit{G}}_{\mathit{c}}$=SU(4), SU(5) (and perhaps ${\mathrm{E}}_6$) are essentially uniquely singled out as possible alternatives of the standard SU(3${)}_{\mathit{c}}$ assignment. The symmetry breaking to SU(3${)}_{\mathit{c}}$ can take place without the introduction of a gauge hierarchy. The consequences of ${\mathit{G}}_{\mathit{c}}$=SU(5) are discussed, including new phenomena which occur between 100 GeV and 1 TeV, and agreement with the standard model at energies below 100 GeV.