Basically, the painter is right. In 9 months, a new paint job has begun to break down. It is a uniform breakdown but nonetheless, a breakdown.
They should be able to 'feather' the color into the original paint assuming they have the same, original paint/color. Sometimes, even a washing of the 'old' paint will make the 'old' stucco look new again, hence, a better match. If you're gonna try a low pressure power washing, I'd do it now before it gets too cold (depending on where you live.) What surprises me is that the contractor is essentially telling you that he can't find out what 'color' was used in the stucco, or what paint was used. The Stucco People should know. Find out where he got his stucco and call them. Tell them the contractor/builder's name and see if they can find out what they shipped him.