Someone might be an expert on the specifics, but what I can say is that the end color is influenced mostly by two things. The color space and tone mapping.
The color space is typically sRGB, and this is likely responsible for your experience with green. sRGB modifies the linear color values into a non linear range that better represent our eyes sensitivity to that spectrum.
Once that has been done, the colors go through tone mapping and post processing. Usually this is to make the image aesthetically pleasing or to match filmic tone mapping, and is rarely kept at natural values.
Long story short, both of those things will screw up any objectivity of the values unless you take them into consideration. Since it’s just math, you can easily convert to and from sRGB, linear or other color spaces, for example.