I think Dennett would understand my point, but as usual he bites the bullet and denies that color is there. He calls it "figment" - figmentary pigment - because according to physics, there is nothing actually blue, inside or outside one's head. But blueness is there, therefore that ontology is wrong.

No it isn't, therefore that 'ontology' is correct. Or so anyone who chooses to do so can argue. If you don't have any better rejoinder than "oh yes it does", then it seems the argument for your position is quite weak.

I think your basic problem is that you really don't seem to have a clear understanding of what you mean when you say a thing is true - thus you have need of terms like ontology.

As I see it, we need only a mathematical description of a set that binds together the various neurological associations we have with a particular input state, and that is the description of 'blue'. There is, quite literally, nothing else to explain.