Heretic of The Seventh Circle
I’ve dived into that phenomenon, including modern remote cultures that have no word for blue as a separate color form green, and in both cases (old and new), there is terminology for different shades of “green” that include “the shade of green that the sky and those one flowers are”, etc.There's a theory that we haven't evolved to accurately understand reality, we've evolved to survive. So the world does not necessarily work the way we think but the way we perceive the world is good enough.
On a related note, ancient Greeks like many old civilizations didn't see the color "blue" because they had no word for it and the sky was just a shade of green.
So, they certainly saw a difference between leaves and the sky, and probably did actually “see blue”.