New U.S. flag just dropped.

No they aren't. "Naming" and "seeing" are two radically different words that mean radically different things. In ancient China, for example, there was no word for green or blue. Instead there was a single word that covered both: 青. (In modern linguistics such terms are called "grue".) You'll find similar things in many other cultures' linguistic history (some even extending to today!).

It doesn't mean they couldn't see the difference. All you have to do to disprove that is look at ancient painted beams in China and see the clearly delineated green and blue segments in complex patterns. If they literally couldn't see blue, this would not exist, yet oddly it does. In fact all they did was classify things differently from modern English. (Today they have 绿 and 蓝 for green and blue respectively, using 青 only for colours like turquoise or the colour of blue-green algae. This is, however, very recent: literally 20th century. The characters have existed for a long time, but were used as shades of 青 for most of that history like we use "sky" and "navy" as shades of blue.)

Trying to claim that they literally couldn't see blue because they named it differently and categorized things differently is risible on the face of it. This would be like me claiming you couldn't tell the difference between sky blue and navy blue because in English they're both called "blue". It takes literally seconds of thought to figure out that this claim is bullshit using just your own language and colour differentiation as the evidence.

There's not much blue in the world other than sea and sky, and those have their own names