Steven Universe AU - Primary Colors

In this alternate universe, divine space beings begin to occupy the planet Earth. Among the many gems, the highest ranked and most powerful were the Diamonds: Red Diamond, Blue Diamond, and Yellow Diamond. These three ruled over the thousands of gems within their rank system, from assistants, to confidants, to supervisors, to generals, to soldiers, and many more. However, despite each Diamond being a powerful authority, they had quite the distaste for one another. They constantly fought about conflicting ideas and therefore resulted in the splitting of the three kingdoms. Any contact with other colored gems was completely forbidden and punishable by death.
For eons, these beings had taken over hundreds of planets, terraforming the land to make more gems, or simply ridding the planet of its original inhabitants to use as their own, building their kingdoms more and more.
When they each stumble upon the puny rock called Earth, they all plan to try and win the planet over, each with their own strategy. However, what the Diamond authorities didn't know was that these humans would put up a fight for their home.