B−R color as a function of the absolute magnitude in the R-band (h = 0.7, K-corrected at z = 0). The symbols for the galaxies are the same as Fig. 2. The linear fit of Niemi et al. (2010) for their (nonisolated) elliptical galaxies from a semianalytic model is shown as a dotted line. The fit for their simulated isolated elliptical galaxies is shown as a solid line. Top and right panels: normalized density distributions of absolute magnitude and B−R color for isolated elliptical galaxies (gray solid histogram) and elliptical galaxies located in the Coma supercluster (red open histogram), respectively. The integral of each histogram sums to unity.