Your point is well taken, and correct, of course. However, "green" is indeed a property (quality) of grass. Grass is green, because it absorbs certain wavelengths of light, such that the remaining light has a wavelength distribution in the visible range that we call "green". So, it's not a feeling that we humans have towards grass, it's a physical property. This physical property is quantifiable and independent of humans.
Now, deciding whether the grass is greener in my neighbors garden, that is getting us into the realm of emotions, because she happens to be quite beautiful 
Absorbing a certain wavelengths and reflecting a certain wavelength is indeed a property of grass (this could be argued though). However, the actual colour we call "green" is the result of the interaction of this reflected wavelength with our nervous system. As such, "green" exists only in our minds (after stimulated by a specific wavelength) and as such is completly personal and only knowable by the individual. Moreover, it is not comparable, so we have no idea if what I call green, is what someone else calls green. The only way to do such a comparison would be to experience someone else's consciousness.
Consider the following hypothesis. Everytime John looks at grass, he actually sees red. His nervous system when stimulated by the wavelength reflected by grass results in an internal mental (visual) experience called red. However, he is not aware of this, since this has been his experience since birth. Mind you, he is not daltonic. It is not that he cannot see green. In fact every time a fire engine goes by, green is the colour he sees.
As he learns to speak, he learns that grass is green and fire engines are red. Therefore he labels his inner visual experiences accordingly. So even though he looks at grass and sees "red", he learns to call that inner experience "green", even though it is red. And of course, he learns to call the colour he sees when he sees a fire engine "red" even though he sees "green".
When he is 18 he gets his driving licence, and he passes with flying colours, by stopping at a red light, even though he experiences it as "green". And he stops at the red light because he has been taught to stop at a red light, and red, is of course the word he uses for "green".
And this is the power and limitation of language. Language creates an illusion of uniformity of inner representations within human beings.
There is no scientific test one could possibly devise to show that John has his inner experience of colours reversed. Language would muddle the issue every single time.
Yet, it is absurd to believe that every single human being experiences exactly the same inner representation when faced with the same stimuli. It is far more likely that we have different gradations of inner experience - perhaps not so drastic as John's.
And this for a pretty objective phenomenon as the result of a specific wavelength on one's consciousness.
Imagine how much more so hopeless is the situation when the concept is completely subjective and culturally ladden as "beauty".
This of course is the same old philosophical problem as "if a tree falls in a forest and there is no one around to hear, will there be a sound?" I happen to be on the side of the people who calim that there will be sound. Sure, there will be vibarations that will be picked up by apparatus palced nearby. But there will be no
sound because I regard sound not as vibrations, but as the inner experience resulting from the stimuli of the vibrations. So to have sound you need both: vibrations and a nervous system to interact with the vibrations and produce a mental representation of it. If there is no vibration (as in the vacuum) or if there is no nervous system (as in Beethoven's ear), no sound.
Best wishes,
Bernhard.
Poll
Topic: are you beautiful