  The aim of this work is to study the evolution of the rest frame color
distribution of galaxies with the redshift, in particular in the critical
interval 1.4<z<3. We combine ultradeep spectroscopy from the GMASS project
(Galaxy Mass Assembly ultradeep Spectroscopic Survey) with GOODS multi-band
photometry (from optical to mid-infrared) to study a sample of 1021 galaxies up
to m(4.5$\mu$m)=23. We find that the distribution of galaxies in the (U-B)
color vs stellar mass plane is bimodal up to at least redshift z=2. We define a
mass complete sample of galaxies residing on the red-sequence, selecting
objects with log(M/M_{\odot})>10.1, and we study their morphological and
spectro-photometric properties. We show that the contribution to this sample of
early-type galaxies, defined as galaxies with a spheroidal morphology and no
star formation, decreases from 60-70% at z<0.5 down to ~50% at redshift z=2. At
z>2 we still find red galaxies in the mass complete sample, even if the
bimodality is not seen any more. About 25% of these red galaxies at z>2 are
passively evolving, with the bulk of their stars formed at redshift z>`3.
