Green isn't entirely up to the brain. The colour depends on how objects reflect the light that we see. Colour is produced by a system of interacting things that includes the brain, light, and the surface of outer objects (such as chlorophyll in leaves). Colour is not a hallucination.

When you say that conscious percepts are arbitrary, you seem to be talking about qualia and the need for some kind of dualism between mind and matter. I agree that we don't understand how consciousness arises from the brain, but it's rational to think that it somehow does so. Thus, consciousness isn't a supernatural substance, but an emergent property of neural complexity.

When you say it's delusory to mistake the map for the territory, I agree that that overconfidence or hastiness can produce unnecessary suffering. That's the great Buddhist insight. But I suspect that that "delusion" is also responsible for technoscientific progress.

By ignoring the metaphysical details and identifying with our limited forms, we have the incentive to learn how they work, to improve our situation. We take up the promethean ambition to progress as a species, rather than just letting whatever happens happen. Of course, those humanistic ambitions might prove to be foolhardy as they seem to be leading to our downfall (the problem of environmentalism). But the point is that these egoistic "delusions" can have positive effects too.