Green leaves on Choisya Sundance

Nothing to worry about - you presumably have Choisya 'Sundance', the yellow leaved version, but those parts of the plant which have not been fully exposed to sunlight or bright daylight because they've been shielded by the outer growth will be green rather than yellow - as the growth you mention is now fully exposed, it will colour up yellow over time. For future reference, if you need to cut back hard, doing that in late April or early May is better - any green growth exposed at that time of year will colour up quicker as there's more exposure to daylight/sunlight than there is at this time of year. If you want the flowers though, then prune immediately after flowering is over.