  We use deep optical photometry from the Next Generation Virgo Cluster Survey
[NGVS] to investigate the color-magnitude diagram for the galaxies inhabiting
the core of this cluster. The sensitivity of the NGVS imaging allows us to
continuously probe galaxy colors over a factor of $\sim 2 \times 10^5$ in
luminosity, from brightest cluster galaxies to scales overlapping classical
satellites of the Milky Way [$M_{g^{\prime}}$ $\sim$ $-$9; $M_{*}$ $\sim 10^6$
M$_{\odot}$], within a single environment. Remarkably, we find the first
evidence that the RS flattens in all colors at the faint-magnitude end
[starting between $-$14 $\le$ $M_{g^{\prime}}$ $\le$ $-$13, around $M_{*}$
$\sim 4 \times 10^7$ M$_{\odot}$], with the slope decreasing to $\sim$60% or
less of its value at brighter magnitudes. This could indicate that the stellar
populations of faint dwarfs in Virgo's core share similar characteristics [e.g.
constant mean age] over $\sim$3 mags in luminosity, suggesting that these
galaxies were quenched coevally, likely via pre-processing in smaller hosts. We
also compare our results to galaxy formation models, finding that the RS in
model clusters have slopes at intermediate magnitudes that are too shallow, and
in the case of semi-analytic models, do not reproduce the flattening seen at
both extremes [bright/faint] of the Virgo RS. Deficiencies in the chemical
evolution of model galaxies likely contribute to the model-data discrepancies
at all masses, while overly efficient quenching may also be a factor at dwarf
scales. Deep UV and near-IR photometry are required to unambiguously diagnose
the cause of the faint-end flattening.
