For this question: Are there Latin words for hair color?, I had to search a little about the concept of "color" in Latin.
I also had a debate on another SE, with people who consider that "color" is only applied to the face, and was a non-existent concept, and "candidus" only mean "bright", with no link with a given color, and that there are mistakes in Gaffiot, Lewis & Short and Oxford dictionaries.
In books and researches papers, they explain that, even if the Latin word "color" can be translated with "colour" (Lewis & Short and Oxford give this meaning, quoting Cicero sentences for instance.), it's only one of its meaning, and the "philosophy" behind the word "color" was different = they are totally different concepts, now and in the past.
From the other discussion, I've found:
The author insists on the difference in the notion of "color" for ancients and moderns, and take the example of flauus, "blond", viridis, "greenish", and caerulus, "deep" (blue), that are linked to precise elements, for which the color is only one of the remarkable properties (respectively here, the hair, the grass, the water)
early 13c., "skin color, complexion," from Anglo-French culur, coulour, Old French color "color, complexion, appearance" (Modern French couleur), from Latin color "color of the skin; color in general, hue; appearance," from Old Latin colos, originally "a covering" (akin to celare "to hide, conceal"), from PIE root *kel- (1) "to cover, conceal, save." Old English words for "color" were hiw ("hue"), bleo. For sense evolution, compare Sanskrit varnah "covering, color," which is related to vrnoti "covers," and also see chroma.
Color in Latin (Latin-dictionary.net)
Color as a verb (dictionary Olivetti)
1 passive form of [colo]
2 (liquid) to strain or to filter, to clarify
3 to purify
4 to remove solids by filter
5 (gold) to wash
Color as a noun (Olivetti):
3 shade, tinge
5 outward appearance or show
6 excuse or pretext
I don't know how they sorted the meaning in those different dictionaries, as they don't give the dates.
color, hue, tint.
1.Coloring stuff, dyestuff:
2. Flowers of varied colors
3. Specif., the natural color of men, the complexion.
In "Embodiment of Latin semantics".
They explain that Romans considered colors a different way than we do, (probably because we have the habits to choose our wallpaper hue on catalog of colors, there's color standard nowadays)
But ancient Romans were referring to colors in comparison with other colors (more reddish, or less yellowish than...) it makes sense. In this book, they call it "a fuzzy set of colors"
Much of the color research carried out in (...) assumes that people have in their minds a "best example" of prototypical color for common color categories, and that they judge an item's membership (to a set) in the color category according to how similar they judge its color is that color prototype"
(...)"The fact that we use a metaphor in English for conceptualizing color relations [I think like "colour ocean"] does not mean that we should expect to find the same metaphor in Latin.
And after, they quote a Pliny extract, where he uses spatial relationship to describe colours... Saying that this coloured impression is "further" from this one. So, here I guess he uses the rainbow as the standard, to mean this impression is further than this one on the rainbow scale (neighbouring colour).
There's a lot more about his conception of colours, but I don't have the full book.
What was the evolution of this term, and the differences with the modern concept?
I tried to find some of them, but I'm not sure I understood all the differences.