  [Background] The recent Jefferson Lab data for the nuclear transparency in
$\rho^ {0}$ electroproduction have the potential to settle the scale for the
onset of color transparency (CT) in vector meson production.
  [Purpose] To compare the data to calculations in a relativistic and
quantum-mechanical Glauber model and to investigate whether they are in
accordance with results including color transparency given that the computation
of $\rho$-nucleus attenuations is subject to some uncertainties.
  [Method] We compute the nuclear transparencies in a multiple-scattering
Glauber model and account for effects stemming from color transparency, from
$\rho$-meson decay, and from short-range correlations (SRC) in the final-state
interactions (FSI).
  [Results] The robustness of the model is tested by comparing the mass
dependence and the hard-scale dependence of the $A(e,e'p)$ nuclear
transparencies with the data. The hard-scale dependence of the $(e,e' \rho ^
{0})$ nuclear transparencies for $^ {12}$C and $^ {56}$Fe are only moderately
affected by SRC and by $\rho^ {0}$-decay.
  [Conclusions] The RMSGA calculations confirm the onset of CT at four-momentum
transfers of a few (GeV/c)$^2$ in $\rho$ meson electroproduction data. A more
precise determination of the scale for the onset of CT is hampered by the lack
of precise input in the FSI and $\rho$-meson decay calculations.
