blue is always blue because it will always have the properties and associations of blue and those are consistent across people because they're the product of systems that plastically shape themselves to be consistent, and any differences are clearly not materially noticeable if they even exist at all.

Good points, though people do not perceive blue the same in the sense of same properties and associations. Humans are no idealized platonic digitalized humans. Being human is concrete materiality and that means that we are each different and bring our own upbringing and past with us.