~~~
I'm not sure why they would have seen it as a murky gray though.
There were a few interesting historical tidbits in the video but it didn't seem to take much of a scientific approach at all.
For example, it is technically possible to be completely color blind and still have vision acuity because of the rod cells in the eye. But it is my understanding that most people who are color blind can still see color, but not all of them, as the video described. This is because there are supposed to be three types of color receptors in the eye, called cone cells. Red, Green, and Blue.
Well, did the Greeks and other ancients just not have blue cone receptors?
I suppose we can't know this without being able to study an ancient Greek subject, but why would many of the populations of the world suddenly develop cone cells in the last 10k years? Doesn't seem likely. So they discuss culture and language as the cause.
If this is the visible light spectrum, and if light works as I understand it, then people with only red cones and green cones wouldn't even know or perceive the higher frequency light waves (left side of the chart), and it all really makes sense. Maybe it's not language at all. I mean, did the ancients have a word for "violet" objects?
Which also makes me ponder the question as to whether it could be possible to perceive even more of the electromagnetic spectrum of you were somehow able to develop a fourth kind of cone receptor; Let's say an ultra-violet cone, for example. Perhaps there is no practical reason to since ultraviolet radiation is harmful to biological cells and the most intense source of it is the sun. But why not infrared cones? Then you could see thermal light, and could hunt more easily at night.