In milder climates of California, where many of us expect at least a few flowers to bloom right through winter, autumn foliar color and colorful winter berries are not appreciated quite as much as they are where autumn and winter arrive earlier, and are cool enough to prevent lingering bloom. Coincidentally, the same mild weather that allows winter bloom here also limits autumn foliar color.
However, mild autumn and winter weather does not inhibit the production of the various winter berries. Such berries can either provide extra color while bloom might be scarce, or at least keep migrating and overwintering birds well fed while trying to do so. Many of us actually grow colorful berries more to keep wildlife happy than to provide color. Some enjoy using them like cut flowers.
It is no coincidence that most colorful berries that ripen in winter are small, red, and profuse. Just like flowers use color to attract pollinators, many types of fruits use color to attract the birds that eat them and subsequently disperse their seed. Bright red happens to work best for that purpose, although there are other options. Small berries happen to be easy for birds to grab and go with.
Most of the specie that provide winter berries are related, within the family of Rosaceae, and most are evergreen shrubs. Of these, firethorn, which is also known by its Latin name of Pyracantha, is the most familiar and most prolific with berry production. The various specie and cultivars of Cotoneaster are not nearly as bold with their berries, but provide a bit more variety of plant form.
English hawthorn and related hawthorns happen to be small deciduous trees that defoliate in winter to leave their ripe berries exposed. Incidentally, as their names imply, both firethorn and the various hawthorns are unpleasantly thorny. The native toyon is a big evergreen shrub that can get almost as big as the smaller hawthorns, and has the potential to be pruned up as a small tree. Hollies are not related to the others, and although very traditional, are unreliable for berry production locally.