Few things that are pointed out that people are misunderstanding.
A lot of our named colors are just hues or shades of other primary colors. We've decided to pinpoint them out. By pinpointing them out we've established them and as such, we notice them more clearly. By calling a specific shade of Red "Pink" we are now more easily able to identify Pink instead of just calling it "light red".
So with regard to ancient cultures - while they did see blue (obviously), they since it didn't make up any sort of important part of their lives--as in their world didn't didn't have a lot of blue things outside of the sky and the ocean, they had no reason to name it. So instead it was simply a shade of a different color and as such didn't have any importance.