  We study the surface of Ceres at visible wavelengths, as observed by the
Visible and InfraRed mapping spectrometer (VIR) onboard the Dawn spacecraft,
and analyze the variations of various spectral parameters across the whole
surface. We also focus on several noteworthy areas of the surface of this dwarf
planet. We made use of the newly corrected VIR visible data to build global
maps of a calibrated radiance factor at 550 nm, with two color composites and
three spectral slopes between 400 and 950 nm. We have made these maps available
for the community via the Aladin Desktop software. Ceres surface shows diverse
spectral behaviors in the visible range. The color composite and the spectral
slope between 480 and 800 nm highlight fresh impact craters and young geologic
formations of endogenous origin, which appear bluer than the rest of the
surface. The steep slope before 465 nm displays very distinct variations and
may be a proxy for the absorptions caused by the $O_2^{-}$ -> $Fe^{3+}$ or the
$2Fe^{3+}$ -> $Fe^{2+} + Fe^{4+}$ charge transfer, if the latter are found to
be responsible for the drop in this spectral range. We notice several
similarities between the spectral slopes and the abundance of phyllosilicates
detected in the infrared by the VIR, whereas no correlation can be clearly
established with carbonate species. The region of the Dantu impact crater
presents a peculiar spectral behavior (especially through the color and the
spectral slope before 465 nm) suggesting a change in composition or in the
surface physical properties that is not observed elsewhere on Ceres.
