Why does the new paint on my car not match the old paint?

Almost always because the repair used the factory paint code without adjusting for how your car has aged. Sun fades pigment over years, so the code describes the colour the car left the factory with, not the colour it is now. A test card compared against the actual panel, in more than one light, is what closes that gap.

Can a single panel be painted, or does the whole side need doing?

A single panel can be painted, but the colour should be blended into the panels either side rather than stopped at the join. Stopping at a seam puts a hard edge next to slightly different paint, which is exactly what the eye picks up. Blending spreads the transition out so there is no line to find.

How long should paint be left before washing the car?

Give fresh paint time to harden fully before washing it, and avoid automatic brushes and harsh chemicals in that period. The workshop that sprayed it will tell you how long for the specific paint system they used — it varies, so ask rather than assume.

All advice

Denting and painting: how a colour actually gets matched

Why the paint code on your door jamb is only the starting point, and what separates a repair you cannot find from one you can see across the car park.

28/07/20264 min readR. Dhandapani

Every car carries a paint code, usually on a plate in the door jamb or under the bonnet. People assume that code is the answer to matching a repair. It is the starting point. The reason is simple: your car has been standing in the Chennai sun for years and the paint that left the factory is not the paint on your car today.

Why the code alone is not enough

Ultraviolet light fades pigment. A five-year-old silver is not the silver in the code, and reds and blues shift the most.
The same code was mixed in different batches at different plants, with small variations built in from the start.
Panels age differently. A bonnet and roof take far more sun than a lower door, so one car can hold two shades of its own colour.
Metallics and pearls depend on how the flake lies, which depends on how the paint was sprayed — not only on what was in the tin.

What a proper match involves

Read the code, and treat it as a family rather than an answer.
Mix a trial quantity and spray a test card, not the car.
Compare the card against the panel in daylight, and then again under a different light. A match that only holds under one light is not a match — this is where most visible repairs are lost.
Adjust the tint and repeat until the card disappears against the panel.
Blend into the adjoining panels rather than stopping at the seam, so the eye never gets a hard edge to catch on.

Ask to see the test card against your car before the panel is painted. It takes a minute and it is the single best predictor of whether you will be able to spot the repair afterwards.

The preparation nobody sees

Most paint that fails does so because of what happened before the colour went on. Panel beating has to bring the metal back to its shape rather than fill the difference; filler is for the last fraction of a millimetre, not for the dent. Primer has to be flatted properly, because every scratch under the colour will show through it in sunlight. And it all has to happen in as little dust as possible, which in this city means indoors.

Questions people ask

Why does the new paint on my car not match the old paint?: Almost always because the repair used the factory paint code without adjusting for how your car has aged. Sun fades pigment over years, so the code describes the colour the car left the factory with, not the colour it is now. A test card compared against the actual panel, in more than one light, is what closes that gap.
Can a single panel be painted, or does the whole side need doing?: A single panel can be painted, but the colour should be blended into the panels either side rather than stopped at the join. Stopping at a seam puts a hard edge next to slightly different paint, which is exactly what the eye picks up. Blending spreads the transition out so there is no line to find.
How long should paint be left before washing the car?: Give fresh paint time to harden fully before washing it, and avoid automatic brushes and harsh chemicals in that period. The workshop that sprayed it will tell you how long for the specific paint system they used — it varies, so ask rather than assume.