I will explain these questions a little further:
Is the green I see the same as the green you see?
The eyes see things in different ways, it is not a mechanical or universal process. Our eyes are recalibrated according to the lighting conditions. The process of white balance occurs constantly in our retina.
If you want a live experience on how the retina modifies this calibration, cover one eye and click on this link: http://www.otake.com.mx/Apuntes/ColorCalibration/Red.phtml
There are also several types of color blindness, for example.
Are the shadows I see at the bottom of the cave the reality?
People see what they know, imagine, deduce from the education they have received. The calibration I mentioned earlier also includes what the brain assumes to be true. You know that a tungsten light is orange, but you do not think about it when you read in such conditions. As a photographer, we are more aware of the big difference in color temperatures in different light conditions, but when you think as a photographer.
Do I need a machine to tell me what I need to see?
Do you want to read the rgb values of the raster file? Do you want all people to use hardware to calibrate their monitors? Should their instructors have certain characteristics? Or it's a psychological question … What do you see?
Do I want you to see the same thing I see?
I want to believe that the photo is taken in conditions of brightness and mediocre quality.
There is chromatic aberration, overexposure, the lens looks dirty or plastic, etc. I want to believe that the person was also negligent in terms of white balance. Do you want to see the case in different terms? Do you want to see the same thing I see?
We will never know. We can probably do an investigation, which will say what the majority thinks. Beyond that, we will never know.
In a bad photo like this … is it important?
I imagine a case where the color of this image is important. "My girlfriend really liked this dress and took a picture". That's it.
It would not be a product, and if it was a case of industrial espionage, the colors would not matter.
Of point of view of commercial photography, you must have a color calibration process, a custom white balance, a calibrated camera, raw files, a color reference photo on the lighting situation, a good color exposure, color calibration monitors, controlled ambient lighting on the retouching studio, a standardized press system … I would say to this picture as it is currently … YOU WILL NOT PASS NOT!