Do you know where you got the stucco colored? They should be able to match it up. Don't expect perfect results though, weather and aging has a way of changing the color. Otherwise I don't see a problem with repairing the stucco yourself.
Also if there is a piece coming off, you might want to bring that to the store to see if they can match it. Might work well even with the weathering.
Good luck!
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