I realized a long time ago that different people likely saw different colors differently. That just had to be the case because I was aware that I couldn’t verify how other people saw them.
You know how you can tell, practically? Discuss whether something is yellow or orange. That I’ve heard come up often.
Greens/blues and teals seem to cause some confusion next.
I don’t have synesthesia, but I do see different colors differently because of the shape of my eyeballs. Green and red. I can see one much better (sharper) than the other. In the days when electric alarm clocks made their way into our bed rooms (late seventies and early eighties that was), you discover such things, certainly if you’ve just been told that you have some astigmatism.
Someone once wrote to me that he sees words in color but also hears them in pitch.
(Not sure who that was. In electronic communications, anyone can pretend to be anyone. I no longer make any assumptions in that area.)