  A universal behavior is predicted for ghost and gluon propagators in the
infrared. The universal behavior is shown to be a signature of a one-loop
approximation and emerges naturally by the massive expansion that predicts
universal analytical functions for the inverse dressing functions that do not
depend on any parameter or color number. By a scaling of units and by adding an
integration constant, all lattice data, for different color numbers (and even
quark content for the ghosts), collapse on the same universal curves predicted
by the massive expansion.
