Because it can be a color term, it's just not always a color term. Just like in English I can use the word "metallic" to refer to a taste, color, smell, or feel

Because it can be a color term, it's just not always a color term. Just like in English I can use the word "metallic" to refer to a taste, color, smell, or feeling depending on context. Translate it literally as "wine-face" and it usually makes sense in English. In the case of the sea, it's referring to its dark wine-like surface. In the case of the cows, it's their ruddy wine-like color. There's also an element of the cows being strong, since wine can create an invigorating feeling in the drinker.