It means, someone who has in control of anything and anyone. Kinda like a manipulator, ruler, or someone who is in charge, but differently y'know?
"She's such a manipulator! She act like she's wearing a red crown!"
The Red crown is something that people might say when talking about someone, someone who is in control, a manipulator, or a ruler. For example:
"Their such a manipulator.. like their wearing the Red crown! Right?"
"Yeah!"