The bimodal feature of the observed local color distribution (Strateva et al. 2001; Baldry et al. 2004; Bell et al. 2004; Giallongo et al. 2005) is also obtained in recent versions of hierarchical models (Kang et al. 2005; Menci et al. 2005; Bower et al. 2006; Croton et al. 2006), so that the existence of two well-defined populations appears to stem from the interplay between the biasing properties of the primordial density field – originating the DM condensations constituting the progenitors of galaxies – and the star formation and feedback processes driving the evolution of baryons in such progenitors.

Despite the above successes in matching the global behaviour of galaxy evolution, when one focuses on the observed proportion of red/blue galaxies, it is found that current hierarchical models underestimate the number of luminous/massive [*red*]{} galaxies. The models (Menci et al. 2005; Croton et al. 2006 with no AGN feedback) addressing the bimodal color distribution of local galaxies are characterized by an excess of massive ($M_r<-22$) galaxies in the blue ($u-r<1.5$) branch of the local color distribution compared to the red one; a similar deficit of luminous red galaxies is present in other semi- analytic models of galaxy formation (Somerville 2004). 