So, subjective color does not exist, but references to color do exist.

The references to red together definitely form a physical network in my brain, right? I have a list of 10,000 things in my memory that are vividly red, some more vivid than others, and they're all potentially connected under this label 'red'. When that entire network is stimulated (say, by my seeing something red or imagining what "red" is), might I not also give that a label? I could call the stimulation of the entire network the "essence of red" or "redness" and have a subjective feeling about it.

I'm certain this particular theory about what "redness" occurs frequently. My question is, what's missing in this explanation from the dualist point of view? Why can't the subjective experience of red just be the whole network of red associations being simultaneously excited as an entity?

Above you wrote

Some people are at the stage of saying, color is a neural classification and I don't see any further problem.

So I guess I'm just asking, what's the further problem? (If you've already answered, would you please link to it?)