  We study colors and metallicities of the Brightest Cluster Galaxies (BCGs)
and Intra-Cluster Light (ICL) in galaxy groups and clusters, as predicted by a
semi-analytic model of galaxy formation, coupled with a set of high-resolution
N-body simulations. The model assumes stellar stripping and violent relaxation
processes during galaxy mergers to be the main channels for the formation of
the ICL. We find that BCGs are more metal-rich and redder than the ICL, at all
redshifts since the ICL starts to form ($z\sim 1$). In good agreement with
several observed data, our model predicts negative radial metallicity and color
gradients in the BCG+ICL system. By comparing the typical colors of the ICL
with those of satellite galaxies, we find that mass and metals in the ICL come
from galaxies of different mass, depending on the redshift. Stripping of low
mass galaxies, $9<\log M_* <10$, is the most important contributor in the early
stage of the ICL formation, but the bulk of the mass/metals contents are given
by intermediate/massive galaxies, $10<\log M_* <11$, at lower redshift. Our
analysis supports the idea that stellar stripping is more important than galaxy
mergers in building-up the ICL, and highlights the importance of
colors/metallicity measurements for understanding the formation and evolution
of the ICL.
