  In hierarchical models of galaxy formation, ellipticals form from the merging
of disk galaxies drawn together by gravity as their surrounding dark halos
coalesce. Using semi-analytic techniques, we are able to follow the merging,
star formation and chemical enrichment histories of galaxies for a given choice
of cosmological parameters. We calculate the ages and metallicities of
elliptical galaxies in a standard CDM cosmology and show that we can reproduce
the observed correlation between magnitude and colour, and the scatter about
this relation. We also study the evolution of ellipticals to high redshift. In
rich clusters, the models predict a substantial population of "evolved"
ellipticals at z>1. However, the average number density of bright ellipticals
must decrease at high redshift. The rate of decrease is sensitive to
cosmological parameters. In a high-density model, the abundance of bright
ellipticals declines by factor of 3 by z=1. In a low-density model (Omega=0.3,
Lambda=0.7), the abundance drops by 30% at z=1, but is down by a factor 3 at
z=2
