Lapis had a blue diamond on her dress, over her stomach area and split in half by her belt. It seemed that in the past, Blue Diamond was in charge of the Earth colony project. I had originally thought that maybe Rose Quartz was an overseer or something similar, who became infatuated with biological life on Earth and rebelled. But if you were to follow the color coding concept to logical conclusions then she would belong to Pink Diamond. Pink Diamond however is listed as a former member... Maybe she was the one who became disillusioned with the Diamond Authority and rebelled, with Rose Quartz and her followers following along? Time will tell I suppose.
Size seems to have an indication of rank in Gem society, with possibly one exception. Diamonds seem to be all huge, tower over everyone. Rose Quartz seemed some sort of leader, and was well taller than a human. Jaspers and other Amethyst are huge, as tall as the fusion Garnet, and hold high rank in Gem society. Pearls are servants, and while tall seem to be very thin. The same is true for Lapis Lazuli, who seemed almost conditioned to obey others, such as Jasper. Finally there are the small, servitor gems like Ruby and Peridot. They seem to be made in mass numbers, like Jaspers and Amethysts, but have no consideration in society... The lowest rung it seems. But then there is Sapphire. She's as small as Ruby, but was an aristocrat, like Rose Quartz presumably was. Just a wild theory, but I suppose it's possible that other Sapphires are not well thought of, but the one who becomes half of Garnet was a special case, due to her future sight ability. We have no real idea if that's a trait of Sapphires, or something unique to her.