In the real world, there is no light frequency associated with "green" and only "green". There are lots of situations that will cause me to experience an object reflecting a single light frequency as different colors.

For example: change the background color or design an elaborate pattern in a picture. There are some freaky things our brains can do (and can be tricked into doing).

There are lots of situations that will cause me to experience an object reflecting a single light frequency as different colors.

Under naively realistic conditions this is a non-issue. If one takes a statistically relevant sampling size of humans at random, and asks them their assessment of the color, they will agree based on its light frequency as the sole understandably relevant qualifier.

Indeed, I am seeing several dozen of those frequencies as I write this.

Frequencies are identified as a spectrum, not as a single point. Furthermore -- you can differentiate from one variety to another. But an objecct which is one variety of green (that occupies one specific point) does not become another variety of green without undergoing a transition event.

If the definition of "grue" is such that the light reflected by a "grue" object is the same frequency at all times, and further that the observer's eyes don't change and more generally that nothing in the world changes,

There's a reason why the paradox's definition completely fails to delve into the physical technicalities of the claim.

This is why I was able to rephrase it with the aled concept.