Question: How do we know that we all see colours the same wayt

Edward Banks answered on 16 Mar 2020:

Awesome question that verges on philosophy rather than physics.
We can’t ever be 100% sure that people experience colours in the same way. The best we can do is induction. Say we define the perfect green to be light with a wavelength of 530nanometers. We could shine some of this green light on someone’s eye, and observe how their eye responds- it will give off certain biological signals. Lets say we also do a brain scan at the same time, and see what signals are firing off in their brain when they see green.
If we repeated this test for a number of people, we’d hopefully see that their eyes and brains were responding in similar ways, which shows that their brain is interpreting the incoming light in the same way. But does their consciousness experience those signals the same? We can’t fully know.
But provided that we all agree that the light is indeed green, does it matter how we perceive it?