  We examined the physical origin of the colour-magnitude relation of
elliptical galaxies in clusters of galaxies in the hierarchical clustering
scenario by using a semi-analytic model of galaxy formation. We particularly
investigate the effects of the star formation process, the supernova feedback
and the UV background on the formation and evolution of elliptical galaxies.
  It is suggested by observation that the colour-magnitude relation reflects
the metallicity-luminosity relation of galaxies, and that for reproducing the
colour-magnitude relation it is important to suppress the chemical enrichment
of stars in faint galaxies. For suppressing the chemical enrichment, we propose
some solutions. One is assuming a strong supernova feedback. Another is
introducing the effect of the UV background radiation. These solutions
degenerate, but they may be distinguished by studying other properties of
galaxies, like the luminosity function, colour distribution, etc.
  Moreover, we find that the supernova feedback model in the starburst which
make the bulge component is important when the star formation time-scale in
disc is longer than the age of the Universe. On the other hand, when the star
formation time-scale is short, the resulting colour-magnitude relation does not
depend on such a starburst model because most of stars are formed not by the
burst but by the ordinary star formation process in disc.
