Historical evidence reveals that humans possess the remarkable ability to render certain physical appearances invisible if they do not focus on them, including something as fundamental as a color.
Homer referred to the ocean as “wine dark”, if you’ve seen pictures of the Mediterranean around Greece, that shit’s as Blue as Blue can be, so what it probably boiled down to is that they could “see” blue, but they always understood it as a blackish color or Green if they had distinguished that by that point.
Basically, there wasn’t a lot of necessity use in distinguishing blue, so most people didn’t until recently.
Homer referred to the ocean as “wine dark”, if you’ve seen pictures of the Mediterranean around Greece, that shit’s as Blue as Blue can be, so what it probably boiled down to is that they could “see” blue, but they always understood it as a blackish color or Green if they had distinguished that by that point.
Basically, there wasn’t a lot of necessity use in distinguishing blue, so most people didn’t until recently.