Board Thread:News and Announcements/@comment-5642360-20180719053217/@comment-34350353-20180721051849

If the diamonds are based off of the four temperaments (which could be unlikely)...

Pink Diamond represents Sanguine because she's very energetic and persuasive as seen in Stevonnie's flashback in Jungle Moon, as well as sociable as seen in Now We're Only Falling Apart.

Yellow Diamond represents Choleric because she's very focused on her goals, as seen in Message Received where she refused Peridot's plans and tells her to let the Cluster emerge.

Blue Diamond (obviously) represents Melancholic, as Rebecca said that blue gems are mainly diplomats, which fits the Melancholic's description of "analytical, detail oriented, and are deep thinkers and feelers."

White Diamond could represent Phlegmatic, which means she's going to be a very calm person.