In the halls there were many different light sources with different temperatures that made finding the correct white balance complex sometimes. This image is one of those.
The car is black with grey contour lines, bumpers and wheel rims. The floor is grey and the posters are printed on white paper. The license plate is made on a white background.
Sounds easy for white balancing, but it isn’t.
From the left side of the car there seems to be a more blue/purple light that gives the left side of the car and the poster behind a blue/purple tint.
In the front of the bumpers you see green reflections that come from a green carpet on the floor. The license plate has got a green tint like the poster on the right side.
And the wall in the top-right corner in the other hall gets a red tint.
Finally I took a white balance from a sample of the radiator next to the Mercedes logo and got a compromise between all those tints.
To be more neutral I used the ‘contrast brightness saturation’. With a parametric mask on the C channel I selected the areas with the lowest saturation and decreased their saturation. That reduced the color tints a lot.
I did this to other photos, too. Sometimes I had to decrease the effect because it looked too unnatural. Think this is more a dirty hack than a solution.
Well, let me see the problem from another perspective…: that car is shiny, and the owner most surely has spent a long time cleaning the tiniest spots, so it’s just like a mirror
An I’m afraid that you can’t remove reflections from mirrors and expect a natural look, so I’ve forget the reflections and have gone to measure the white balance from a matt surface: the grey upholstery on the back seat. From then it has been just removing fringes and enhance the black color of the car.
By the way, this time the R&L post-resize sharpening halos have helped to enhance the chrome-plated areas.
Here is a GIMP +RT5.7 version. The trick is to desaturate only the car and floor and the white parts of the posters using mask (and be clever enough to keep the blue reflection on the bonnet and the color part on the number plate untouched!).
