[@Archmage MC]. . . why are you calling Pink Diamond 'Red'?

Edit: To add on to the Theory crafting, i figure that Pink Diamond's mural lacks a glow because, well, she ded. Also, maybe she was the least interested on conquering other planets, hence only having the Earth.

Edit #2: Also, I wonder if the circles behind each of the Diamonds heads have anything to do with anything. They seem a bit too prominent to be nothing, especially given the varying sizes between White/Pink Diamond's circles against Yellow/Blue Diamond. Perhaps it's a simple of their level of power or status within the Crystal Empire(which would be interesting if the Diamon with the least amount of planets shares a similar amount of influence to the Diamond with the highest amount of Planets)

Edit# 3; Archmage's ideas bear some merit, baring the first one as it seems a bit out of character for Gem society, plus I doubt Yellow Diamond would be happy about having planets given to her. She seems much too proud and stuffy to accept hands out, and besides that, they'd probably be more even if that was the case, so as to not promote favoritsm(which would clearly be towards White Diamond if that was the case). Her Being the youngest seems interesting, but given how little we know about where the Diamonds fit into everything(if something is revealed in the leaked episodes, don't tell me, I haven't and won't be seeing them until they're made available legally)