NUV – R rest frame color (dust corrected) of galaxies within X-ray selected groups versus stellar mass. Red diamonds and blue dots circles mark the classification as passive and star-forming galaxies according to the spectrophotometric flag in the photometric catalog. Passive galaxies overlap with the associated sequence of red galaxies identified in rest frame NUV – R > 3.5 and marked by the vertical line (Ilbert et al. 2009). The solid horizontal line marks the completeness stellar mass for passive galaxies at each redshift.