All these questions about colour perception lately have, apart from annoying me (do people really think that human physiology changes that much from one millennium to the next, or that language is that central to cognition?), reminded me of another old chestnut about ancient Greek colour terms: that Homer's word for the colour of the sky was "bronze". It's a related thing: supposedly, since he had no word for "blue", they had to call it "bronze" instead.
Well, the fact that I'm posting about it probably lets you know in advance that it's not true. Homeric epic does indeed refer to "bronze sky" three times (Iliad 5.504, 17.425; Odyssey 3.2) but there's absolutely no reason to interpret it as a colour term. It becomes a bit more obvious if you look at other uses of "bronze" as an adjective. First, Iliad 18.222:
ὄπα χάλκεον Αἰακίδαο
the bronze voice of Achilleus
Similarly Iliad 5.785:
Στέντορι εἰσαμένη μεγαλήτορι χαλκεοφώνῳ
...making herself look like the great-hearted bronze-voiced Stentor
(I guess this is where we get "stentorian"?) Next, Iliad 11.241-2, the death of Iphidamas:
ὣς ὃ μὲν αὖθι πεσὼν κοιμήσατο χάλκεον ὕπνον
οἰκτρὸς ἀπὸ μνηστῆς ἀλόχου...In this way [Iphidamas] toppled and fell into a bronze sleep, pitiful, away from his wedded wife...
And Iliad 5.704:
χάλκεος Ἄρης
bronze Ares
It should be pretty transparent that the meaning is in figurative. In these passages it evidently means "pitiless, terrible". That being the case, it'd be daft to assume that when it gets used of the sky it suddenly turns into a colour term. Exactly what shade of metaphor we're looking at in the "sky" passages is open to debate, though. It could be "pitiless, terrible" as elsewhere, making "pitiless sky" a pathetic fallacy. It could mean "bright" or "strong". It could be a reference to the "bronze-pathed house of Zeus". One alternative that I find appealing, if not exactly compelling, is that it could be a reference to an upturned cauldron, for which one word was χαλκίον.
Finally, as a matter of interest, the same metaphor appears in the Hebrew bible in Deuteronomy 28.23:
The sky over your head shall be bronze, and the earth under you iron.
I don't think anyone's ever taken that as a reference to the colours of the sky and earth.