Left panel: redshift distribution of the zCOSMOS-bright galaxies (black). Red points represent group member galaxies with spectroscopic and photometric redshifts as obtained from our algorithm. The cyan solid line and the violet dashed line correspond to the two different magnitude cut-offs adopted to define the volume-limited samples of the low- and high-redshift bin respectively, see text for details. Central and right panel: (U − B) rest-frame color versus mass for the lowest and the highest redshift bin. The blue dashed line corresponds to the color-dependent ℳ_{cut − off}, while the red solid line corresponds to the fixed ℳ_{cut − off} for our mass volume-limited sample. The red dot-dashed lines highlight the mass ranges adopted in the mass-segregation analysis, see Sect. 6.5 for details. The cyan dotted line corresponds to the separation between red and blue galaxies (see text for its precise definition).