Phlox subulata (creeping phlox, moss phlox). Comes in pink, white, pale lavender - think there's even a white with pink candy stripe. Once established, it'll cascade over a retaining wall. Nothing eats it; will often put out a light second bloom late summer, early fall and stays green for me all year around.

There's also arctostaphylos uva-ursi (bearberry), or one of the creeping sedums like Drgon's Blood. No wildlife seems to bother either of those.

Another idea is Veronica prostrata. It has a trailing habit, and my deer have never eaten them. Aztec Gold has chartreuse leaves and blue flowers. Royal Blue and Crater Lake Blue have green leaves and blue flowers.

Deer eat my sedum, but I do see trailing ones growing on retaining walls around here. Some sedums are fast-growing. The Dragon's Blood sedum I bought (which may not be the same "Dragon's Blood" another person has) grows very slowly.