If you want to see something green in winter, kerria is a good place to start (If you can find K. japonica 'Picta', snap it up; the variegation is really nice the rest of the year...)

Stewartia is beautiful on the trunk and bigger branches (tri-color patches). My experience is with S. pseudocamelia (Japanese), but Michael Dirr says that those in the Mid-Atlantic and South should give S. monodelpha a try (better heat tolerance).