On her grand throne she sits,
She is leader of the Gray
during the evening, black as the shadows that gather.
Evening = bronze marking from Earth God, black = coat color
Under the dying sun,
Fluff
the Queen, born and raised,
Paladin the Valiant was a leader of a herd, so born to a leader.
is told she should clean her sword.
Three references in this clue: clean (dirty) = red tip, sword = unicorn, sword = warrior personality
"Why?" she asks. "Fly your banner and show your colors!"
Show your colors- instead of being Gray!