Vinca minor would be good, as it spreads. There's a varriegated form which is pretty all the year round, called 'Illumination'.There are also purple and white flowered Vincas .You could also plant prostrate evergreens such as Juniperus squamata, Cotoneaster dammeri and Ceanothus thyrsiflorus repens. The last two flower, and the Cotoneaster has small red berries, too.

I hope this helps.

Yes, Cotoneaster is excellent for slopes. You could also try something ground-hugging like Ajuga reptans, which spreads very easily and has bronze leaves.