12:3And another sign appeared in heaven: and behold, a great red dragon having seven heads and ten horns, and on his heads were seven diadems.

And ANOTHER SIGN appeared in heaven:

The woman (verse 1) was the first sign.

and BEHOLD, a GREAT RED DRAGON

"Look at that", John says, "I have seen evil in my day, but seeing this makes me realize evil is much larger and pervasive than really known." Even John is taken by the "size of evil"; we just don't experience that in our everyday activities. Nonetheless, evil of that magnitude is around us all the time.

Red is the absence of peace (Revelation 6:4); so all turmoil and conflict is embodied in this SIGN (symbol).