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The paint manufacturer's codes as shown in the table (like the WA Code 307D shown on the RPO sticker) are for paints that are mixed to match as close as possible to the paint colors used at the Assembly Plant.
A good paint shop will match the existing paint as best they can by mixing additional tints to achieve a good match. Some shops will mix paint on site using a computer system and racks full of tint that go into a base just like is done at Lowe's or Home Depot.
Obviously, the existing paint color on a car can change from excessive sunlight, lack of waxing or a good sealant, damage from chemicals in the air and other things. A good painter will make adjustments to get the new paint to look "right".