You'll probably have to use foliage colour because not a lot of flowers will be produced by plants at that time of the growing year.
Bedding plants could be used but these always have a downside - they're shortlived and need replacing each season - this is not cost effective and tiresome.

There are though evergreen clematis that flower from Dec-March - the balearica types for example.

Depends on the size you want really,but basically evergreen shrubs, particularly variegated ones like Euonymus fortunei varieties, Euonymus japonica, Pieris 'variegata' and Skimmias. Note the last two require acid soil and some shade.