There's something of a cultural element to colours. Some cultures recognize blue-green as a separate colour from either component. And while violet and indigo are physically distinct, they just look like lighter and darker versions of the same colour to me. So I think the answer would be somewhat subjective.
It would also probably be harder to distinguish differences at the same resolution as visible light when it came to very high or very low EM wavelengths.
Some cultures recognize blue-green as a separate colour from either component
I've heard that in Japanese everything from blue to green (including cyan, seafoam green, etc.) is simply lumped under one word but I don't know how true that is.
Japanese started using the word 緑 "midori" to mean green after the war and increased contact with western countries. The word midori used to refer to freshly growing plants, like the English words greenery or flora. Otherwise both blue and green were 青 (ao) until pretty recently, with green considered a particular shade of blue. And weirdly even though the word midori used to literally refer to vegetation, the word ao (blue) is still used to refer to vegetables or plants as green.
This mirrors what happened in Chinese too, even with the same characters, although I'm not sure when Chinese started separating blue-green.
There's something of a cultural element to colours. Some cultures recognize blue-green as a separate colour from either component. And while violet and indigo are physically distinct, they just look like lighter and darker versions of the same colour to me. So I think the answer would be somewhat subjective.
It would also probably be harder to distinguish differences at the same resolution as visible light when it came to very high or very low EM wavelengths.
I've heard that in Japanese everything from blue to green (including cyan, seafoam green, etc.) is simply lumped under one word but I don't know how true that is.
Japanese started using the word 緑 "midori" to mean green after the war and increased contact with western countries. The word midori used to refer to freshly growing plants, like the English words greenery or flora. Otherwise both blue and green were 青 (ao) until pretty recently, with green considered a particular shade of blue. And weirdly even though the word midori used to literally refer to vegetation, the word ao (blue) is still used to refer to vegetables or plants as green.
This mirrors what happened in Chinese too, even with the same characters, although I'm not sure when Chinese started separating blue-green.