Okay, before I start I'd just like to say that I really hope no one's come up with this theory yet. That would be really embarassing. But if they have, I'd like to know so I can see if I missed any evidence or if I found something that they haven't.
Alright, so you all remember Watermelon Tourmaline, don't you? She's the pufferfish from Beach Party.
Five episodes later, in Monster Buddies, a gem was shown with a very similar color scheme.
What does this resemble? The symbol that fans have been speculating about since Serious Steven, which is assumed to represent the current Great Diamond Authority. I know that the creators take great care in selecting the right gems for their characters (assuming Matt's comment about throwing darts at a board with gem names on it was just a joke) so the gem chosen for this character will have a special meaning related to the character.I did some research, and it turns out that Watermelon Tourmaline is said to "remove imbalances (and guilt) caused by conflicts and confusions"
Then I realized that the gemstone I think belongs to WT is split between the two colors instead of having them in rings like this type of gem usually does. The colors that it's split between also stood out to me.
I think that the pink represents Pink Diamond (who is widely theorized to be Rose Quartz) and that the green represents the other diamonds (yellow, blue, and white). Together, the two colors represent the two sides of the war. In a way that ironically echoes the real life gem's assosiations, Watermelon Tourmaline was conflicted and confused about which side to take. What if that caused her to be corrupt? What if all corrupt gems are the way they are because of some kind of inner turmoil?
So, what do you think about my theory? Have anything to add? Found any holes in my argument? Please comment below! :D