Jamieson, Fausset and Brown on Revelation 12:3

3. appeared--"was seen."

wonder--Greek, "semeion," "sign."

red--So A and Vulgate read. But B, C, and Coptic read, "of fire." In either case, the color of the dragon implies his fiery rage as a murderer from the beginning. His representative, the beast, corresponds, having seven heads and ten horns (the number of horns on the fourth beast of Da 7:7; Re 13:1). But there, ten crowns are on the ten horns (for before the end, the fourth empire is divided into ten kingdoms); here, seven crowns (rather, "diadems," Greek, "diademata," not stephanoi, "wreaths") are upon his seven heads. In Da 7:4-7 the Antichristian powers up to Christ's second coming are represented by four beasts, which have among them seven heads, that is, the first, second, and fourth beasts having one head each, the third, four heads. His universal dominion as prince of this fallen world is implied by the seven diadems (contrast the "many diadems on Christ's head," Re 19:12, when coming to destroy him and his), the caricature of the seven Spirits of God. His worldly instruments of power are marked by the ten horns, ten being the number of the world. It marks his self-contradictions that he and the beast bear both the number seven (the divine number) and ten (the world number).