A couple of years ago I was travelling through India and I noticed that the cows in the fields had red horns. Amazing, I thought that there were species of cows with red horns until it was pointed out to me that they were in fact painted. In this passage where the inseparable Ajaxes are compared to oxen pulling a plough, the oxen are described as wine-dark. I can find no evidence that the Greeks habitually painted their animals’ horns but perhaps they did and this is why they were described as wine-dark.
Αἴας δ᾽ οὐκέτι πάμπαν Ὀϊλῆος ταχὺς υἱὸς
ἵστατ᾽ ἀπ᾽ Αἴαντος Τελαμωνίου οὐδ᾽ ἠβαιόν,
ἀλλ᾽ ὥς τ᾽ ἐν νειῷ βόε οἴνοπε πηκτὸν ἄροτρον
ἶσον θυμὸν ἔχοντε τιταίνετον: ἀμφὶ δ᾽ ἄρά σφι
πρυμνοῖσιν κεράεσσι πολὺς ἀνακηκίει ἱδρώς:
τὼ μέν τε ζυγὸν οἶον ἐΰξοον ἀμφὶς ἐέργει
ἱεμένω κατὰ ὦλκα: τέμει δέ τε τέλσον ἀρούρης:
Ajax, the swift son of Oileus, never stood separate from Ajax the son of Telamon not even a little, but they were like a pair of wine-dark oxen in a fallow field that with equal strength pull the fitted plough. Much sweat is churned up at the base of their horns. The single well-polished yoke keeps them apart as they struggle through the furrow, and so the plough cuts through to the turning point of the field.