Plum and olive weddings are gorgeously rich. They are particularly ideal for an autumn or winter wedding because of the warmth of the colours. On paper, this colour combination might seem radical, but when executed properly, it looks exceptional. Just keep to the dark, muted tones of plum and moss or olive to avoid bight purple and green.
For a plum and olive wedding, less is more. Your primary colour would work better as plum. That way your olive shades can act as "the greenery" to the overall plum effect.