Once green always green

"Long before time had a name, Ninjago was created by the First Spinjitzu Master, using the Four Weapons of Spinjitzu. The Scythe of Quakes, the Nunchucks of Lightning, the Shurikens of Ice and the Sword of Fire. Weapons so powerful, no one can handle all of their power at once! When he passed away, his two sons swore to protect them, but the oldest was consumed by darkness and wanted to possess them. A battle between brothers broke out, and the oldest was struck down and banished to the Underworld. Peace returned, and the younger brother hid the weapons, but knowing his older brother's relentless ambition for power, he placed a guardian to protect them. And for fear of his own demise, a map for an honest man to hide. That honest man was your father. The older brother is Lord Garmadon, and I... need to find those weapons before he does."
—Sensei Wu, Way of the Ninja