[mortify]

Although not truly the point... we do know that people don't seen red and green flipped because color's don't work in isolation. It's also how they work together. If a person with flipped red/green mixed what they saw as red (actually green) with blue, they wouldn't get purple.

We could suppose that someone could see the entire spectrum inverted, but that causes other problems that we could test for. There are more hues between red and blue than there are between green and yellow. Instead of seeing brown (really dark yellow), they'd see dark blue.

[somenameforme]

The point he's making is that colors do not "really" exist - they're simply different levels of energy on the electromagnetic spectrum. How we perceive those colors is exclusively a product of our brain using input filtering from our eyes and then converting this into signals that we then perceive. But there's no reason to think that this processing and filtering eventually results in the exact same perceived color for every person. My red, blue, and purple could all be perceived simply differently than yours - even though every physical law interacting with what we perceive as color would behave identically.

And the even more interesting thing is that this nuance of reality extends to everything. The world as we perceive is only after extensive processing and filtering by our brain, driven by millennia of evolution. And it's very safe to say that our perception of the world has changed over those millennia and will continue to change in the future. So it seems essentially illogical to then assume that everybody at the current time shares the exact same 'experience' of perception.

[mk12]

Yeah by "my red" I'm talking about qualia as in the knowledge argument https://plato.stanford.edu/entries/qualia-knowledge/

[OJFord]

You're just introducing more and compound things that we don't know if we have the same experience of.

Consider an enum type: we agree on labels (colour names) for different stimuli; as those stimuli combine they correspond to some other enum variant, and we interpret them as the same label. But we don't know, and I agree with the top-level comment that we can't know, whether our perception of the stimuli with that label is the same.

This is distinct from colourblindness, which is inability to distinguish stimuli for some of the enum variants, and so the labels get merged/boundaries between labels move. (Ok fine we also need a hashmap from stimuli to the enum..)

We agree to call the rose pink, and it's the same pink we see when we look at a colour card and agree it's the colour of the rose, but we don't know that what our brains reconstruct from the light when we look at 'pink'-labelled things is the same.