Why Esau and All of Edom Are the Color Red

"To the land of Seir, the field of Edom." [What is the meaning of "to the land of Seir"?] That he makes the hair (se'ar) of a person stand on end. "The field of Edom" — he is red (adom), and his food is red, and his warriors are red, and his clothing is red, and his shields are red, and his land is red, and the one who stands against him is red, and the one who exacts punishment from him is red, in red clothing. He is red, as it is said: "And the first came forth ruddy" (Genesis 25:25). And his food is red: "from this red, red stuff" (Genesis 25:30). And his warriors are red: "The shield of his mighty men is reddened" (Nahum 2:4). And his clothing is red: "the men of valor are clothed in scarlet" (Nahum 2:4). His shields are red: "The shield of his mighty men is reddened" (Nahum 2:4). And his land is red: "to the land of Seir, the field of Edom." And the one who stands against him is red — this is David: "And he sent and brought him, and he was ruddy" (1 Samuel 16:12). And what is written concerning him? "And he put garrisons in Edom" (2 Samuel 8:14). And the one who exacts punishment from him is red: "My beloved is dazzling and ruddy" (Song of Songs 5:10); "Who is this coming from Edom?" (Isaiah 63:1), in red clothing: "Why is your clothing red?" (Isaiah 63:2).