What is the right way to quench star formation in semi-analytic model of
  galaxy formation?
  Semi-analytic models of galaxy formation are powerful tools to study the
evolution of galaxy population in a cosmological context. However, most models
over-predict the number of low-mass galaxies at high redshifts and the color of
model galaxies are not right in the sense that low-mass satellite galaxies are
too red and centrals are too blue. The recent version of the L-Galaxies model
by Henriques et al.(H15) is a step forward to solve these problems by
reproducing the evolution of stellar mass function and the overall fraction of
red galaxies. In this paper we compare the two model predictions of L-Galaxies
(the other is Guo et al. , G13) to the SDSS data in detail. We find that in the
H15 model the red fraction of central galaxies now agrees with the data due to
their implementation of strong AGN feedback, but the stellar mass of centrals
in massive haloes is now slightly lower than the data. For satellite galaxies,
the red fraction of low-mass galaxies ($\log M_{*}/M_{\odot} < 10$) also agrees
with the data, but the color of massive satellites ($10 < \log M_{*}/M_{\odot}
< 11$) is slightly bluer. The correct color of centrals and bluer color of
massive satellites indicate that the quenching in massive satellites are not
strong enough. We also find that there are too much red spirals and less
bulge-dominated galaxies in both H15 and G13 models. Our results suggest that
additional mechanisms, such as more minor merger or disk instability, are
needed to slightly increase the stellar mass of central galaxy in massive
galaxies, mainly in the bulge component, and the bulge dominated galaxy will be
quenched or then be quenched by any other mechanisms.
