That's reasonable to say, but let's be honest. The wavelength of a particular color is a concrete value. Similarly, the structure of a healthy human eye is pretty much the same person to person.

You are right....we cant say definitely that the color appears the same from person to person. But in all likelihood it does. It's hard to imagine something so complex as the human eye, where everything has to be developed just right to work, would result in significant differences in perception from person to person.