We had a standard sized GG tree when I was a kid right on through college. Mom made all sorts good tasting things from the sweet golden apples. However, whenever I see them for sale at produce stands, they are green as can be.
I came across an old USDA article on how to harvest and store apples. It said once Grimes goes into cold storage, it will never turn yellow once you then put it back at room temperature. That apple needed to be picked firm and green as it starts to drop and is too soft for commercial harvest as it turns yellow on the tree. Nowadays there are stop drop growth regulators that could be of use.