Apparently different languages have different numbers of important colour words, and which colours will be included progresses in a predictable way, so that for example, if there is a word for red there will be a word for blue but not necessariy vice versa. I'll try and find my reference for this.

yes, I have seen/read discussions about this.
It usually starts with Homer– and his "wine dark sea" and did the Greeks see the colors blue and red as being shades of the same color– since wine tends to be red.

Wine stains, and the stains can start red, and then dry to blue– so characterizing red as being a shade of blue is not as hard as we might think.( See more on this below)

But I have always thought he was comparing the normally clear water of the Aegean with the muddied waters of a storm– and the sea was dark with sediment as wine is dark with sediment, rather than the color...

Color is just a specific frequency of light, that the human optic nerves respond to in almost the same way, but how we label the resulting color is cultural. Is teal green or is it blue?

There are also certain dyes for silk, that are like a litmus paper– the pale sky blue dye changes color as it ages and goes to a pale lavender, and then to pink–one of my first silk blouses had this characteristic.
And this sort of color change also occurs in nature...

It is interesting to look at crayons, or other art material and see the names colors are given. Some are pretty clear cut– titanium white, or chrome yellow, but ‘sky blue"? Or taupe? Some colors, to me, that have a very specific meanings –Ecru which is raw linen color– also known as tow (as in "tow haired boy with cheeks of tan"(Walt Whitman?))have come to mean any number of shades of pale beige.

Well to be honest, tow is unspun linen, and spun and woven linen is ecru..and they are not quite the same color, but they are very close.