So why do the car manufacturers have so many variances? Most car manufacturers have three major paint suppliers. The manufacturer decides on a standard color for production and submits a painted sample to their suppliers. The paint manufacturer then produces a formula for the “standard sample” and is allowed a tolerance of plus or minus 5% when they deliver the paint.
This is the first problem because the plant in the east coast may be getting a 5% shade greener on a blue metallic standard and the plant in the west coast may be getting a 5% shade violet on the same blue metallic standard. When compared side by side, they look like a completely different color. This is the reason the paint manufacturers usually have the standard formula followed by two alternates. If the alternates are not available, the painter in the body shop usually mixes the standard formula and tints it accordingly.
The second reason for variances in paint colors is the metallic color applications. The metallic colors are now classified in 7 categories. Extra fine, fine, medium, medium coarse, coarse, and extra coarse. The metallic colors control the value (lightness and darkness) of the color similar to what white does in a pastel color.
Metallic colors will cause variances in color when applied. Temperature, paint film thickness, flash off time between coats, fluid tip sizes, speed of the spray gun, surface type (Plastic or Metal) and humidity will all cause the color to shift lighter or darker.
The rule of thumb: the longer it takes to dry, the darker the color will change as it dries. This is caused by pigment floatation. The metallic flakes will settle down to the bottom of the paint film and push the pigment up causing the color to shift darker.
The reasons above only mention the variables at the car manufacturers level. So what happens to a color after three years of sunshine? Many people think that colors do not change, but they do, and I will prove it. If you own a car that is at least three years old and has been out in the sun most of the time, remove a pinstripe and you will see the original color when you bought the car.
The sunlight has ultra-violet, and has absorbed some of the pigments. Blue metallic colors sometimes shift to a greener shade, and reds will turn pinkish or more orange. The auto body shop has to deal with matching an oxidized color in addition to new OEM colors. The new paint to be applied will look brighter and cleaner but the rest of the car looks dead even if you polish it.
Auto Body Shops today have a greater challenge than just color match. The texture or (Orange Peel) also has to match the original finish in order for it to look pre-accident condition. This can be accomplished by using the proper spray gun, polishing equipment and experience.