I can't help being reminded of the passage in the book of Revelation where John describes the throne room of God, and he notes "a rainbow round about the throne, in sight like unto an emerald".
That's a little hard to imagine, because a rainbow contains a full spectrum of colours, whereas an emerald usually has a single colour, so some translations interpret the rainbow as being like the shine/gleam/glow of an emerald. But the idea that at infinite energy a spectrum might be perceived to human eyes as a single bluish hue is a nice thought, like the coincidence(?) that this colour happens to look like a clear summer's sky.
Anyway, for comparison, here's an image from Wikipedia of a synthetic emerald:
The Greek term here is "ἶρις κυκλόθεν"[1]. According to Liddell-Scott "ἶρις" ("iris") may not only mean specifically the rainbow, but "any bright-coloured circle surrounding another body"[2]. So the emphasis is not on the spectrum, but on the shape. A better translation would be: "and the throne was completely surrounded by an emerald circle."
Probably many, but my understanding is that the prophets "visions" aren't really meant to be taken literally: god is supposed to be this thing outside of reason and perception (not a "thing" actually), the visions are what the prophet's human mind makes up: throne, gold, rainbows and stuff aren't what the divine _actually_ is, it's just how the prophet's human mind visualises it. Also sometimes descriptions of visions are symbolic, which means these descriptions are as far from the vision as the vision is far from "actual" god.
(History of God is an interesting book, even/especially for atheists)
It's a nice thought, but describing the color in the OP as emerald seems like it would be a fairly poor attempt at describing your vision. It's more of a cornflower blue, or even as you say (and something easily accessible to the ancients): the color of a clear summer sky.
For example if I was John and I saw the color of infinite temperature around God's throne, I would probably say something more like:
> and there emanated from the throne an incredibly bright blue halo, as if a clear summer sky was shooting forth from God's throne.
Different cultures distinguish colours into different classes. You can do an experiment where you give a person sheet of randomly colored pages and ask them to divide them into named stacks.
A western civilisation member might do something like Red, Brown, Orange, Yellow, Green, Blue, Pink, Violet, Grey and perhaps do something special with White/Black. (11 basic colours)
A Russian will most likely split blue into light blue and dark blue. (12 basic colours)
Himba people have 5 basic colours:
Serandu – used to describe reds, browns, oranges and some yellows
Dambu – includes a variety of greens, reds, beige and yellows
Zuzu – used to described most dark colours, black, dark red, dark purple, dark blue, etc.
Vapa – used for some yellows and white
Buru – used to describe a collection of greens and blues
When I was a kid, it was "obvious" to me that dark green and light green were two completely different colors, and it frustrated me to no end that people wouldn't agree with me, yet insist that pink and red were different colors.
It’s a majorly weird thing. Knowing of a colour makes it obvious, but not having the concept embedded into your neurons means it isn’t split and out and distinguished when you experience the world. There are some African tribes with a very different knowledge of blue and green to us that makes the contrast very clear
There is much confusion about the Greek color theory, and I can imagine that for this reason there is also lots of confusion about which word is used for which color. The Greeks with their arts were merely interested in representing humans accurately and not interested in making landscapes. This might also explain why there is not much attention for the color blue in the writings that survived from that time period.
That's a little hard to imagine, because a rainbow contains a full spectrum of colours, whereas an emerald usually has a single colour, so some translations interpret the rainbow as being like the shine/gleam/glow of an emerald. But the idea that at infinite energy a spectrum might be perceived to human eyes as a single bluish hue is a nice thought, like the coincidence(?) that this colour happens to look like a clear summer's sky.
Anyway, for comparison, here's an image from Wikipedia of a synthetic emerald:
https://en.wikipedia.org/wiki/File:SyntEmerald_0302.jpg