Yep, absolutely hold out for what you want. If you don't want silver, don't get the silver, same price or no. Even if the dealer can't get the car locally, they can certainly order a black one and I definitely would not pay more than your previously negotiated price. Sounds like a bait & switch to me too.

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2005 X3 3.0i, manual, mystic blue, matte titanium interior trim, gray leather (premium pkg), heated seats, chrome exhaust tips!