You pay a visit to the auto parts store for some touchup paint. You’re careful to get the correct number from the plate inside the driver’s side door, knowing that paint with the corresponding number we’ll give you a match. You feel pretty good about yourself on the way home from the store. You’re looking forward to touching up those spots and making your car look brand new.

Then it happens.

You discover the paint in the bottle doesn’t match the paint on your car. You suddenly become painfully aware that auto body color matching isn’t as easy as it sounds. But where did you go wrong? You wrote the number down correctly. You bought the right paint from the auto parts store.

Not an Exact Science

First off, you didn’t do anything wrong. Auto body color matching is not an exact science. There are many things in play that can affect the match when car owners purchase touch up paint and apply it themselves. Here are just a few of them:

• Paint Formula – Car manufacturers create their own paint formulas every year. But those formulas aren’t perfectly consistent from one bash to the next. If your car was the first one through the paint shop after the staff changed colors, there may be a bit of residue from the previous color mixed in with your paint job.

• Temperature and Humidity – The temperature and humidity of the paint shop will affect the final color a car displays when it dries. Even slight variations can make quite a bit of difference.

• Environmental Conditions – Over time, the paint on your car will change slightly due to environmental conditions. It’s almost guaranteed to fade in the sunlight. It can also be discolored by salt, chemicals, etc.

The fact is that there is no such thing as a 100% match for auto body paint. If you don’t have the original batch of paint and the exact same conditions in the body shop, you won’t get perfection. So how did the pros do it?

Eyeballs and Cameras

Auto body color matching in a pro shop is about two things: eyeballs and cameras. A professional auto body technician can match the paint pretty closely, but probably not perfectly. To start, he selects the right base color by doing the same thing you did: checking the number you found inside the door and then finding a paint with the corresponding number.

Next, a little bit of that paint is sprayed on to a card and allowed to dry. The technician then compares it side-by-side with the paint on your car. If it doesn’t quite match, he uses a special camera and software to take a picture and analyze the color of the paint. Data from that photograph can be used to modify the base color accordingly.

This process of eyeballing and taking a picture repeats until the technician can’t see a difference between the two colors with his own eyes. It’s still probably not perfect, but it’s close enough that no one will be able to tell.

A Keen Eye Is Key

When all of said and done, the human eye can perceive minute subtleties in shade, hue, and tone. So it takes a keen eye to get colors to match in the auto body shop. Needless to say that shop owners are pleased when they have a good paint technician on the team. A technician with the right knowledge, skill and eyes can master auto body color matching as well as it can be mastered.