So, my suggestion I think you have to calibrated it.
This is done in PS. As you can see, also mathematically, the corrected version has a better white balance =)
On my eyes, the original version has some "green tint" applied. Also for PS and for my monitor.
But the author did this expressly.
Cecofuli, I often discuss about this with some friends, 3d artist and photographers. Tecnically, you are right, the area you've selected to set white point is not balanced, so you've calibrated all the image to make the point become white. I don't agree in this, for some reasons: the green surplus you have in the selected area has caused by the reflected colour in that particular area, and is not correct to calibrate all the image on this value. Also, actually this material is white, but also in 'nature' it is alterated by the colours all aroud, so actually also in real world you don't see it white. And this is the question: is it right to calibrate all the image for this whit area point or is it better to leave the natural color distribution on all the image?
I think there is not only one right answer, but I like to talk with you friends about this.
Have a nice day!
(Maybe we can move this discussion in an other place, Ondra?!?!)