Blue Pearl was the prized servant of Blue Diamond. Her trusted confidant, Blue Pearl was unique among the other pearls, as she was highly valued beyond mere utility, to the point where Blue Diamond was willing to die for her.
Her height and physical frame are identical to that of the Crystal Gems' Pearl and Yellow Pearl; she is altogether very lean, with long legs and arms, and has a tall oval-shaped head with a prominent and pointed nose. She has sky blue skin and chin-length, messy, periwinkle hair. The upper portion of her face is covered by her bangs, similar to how her owner Blue Diamond covers her face with her hood. It is revealed in Gallop to the Gala that she only has one eye, much like Sapphire.
Her outfit consists of a periwinkle bodysuit with an open diamond-shaped keyhole neckline, similar to Yellow Pearl's, a knee-length, frost blue, sheer skirt, and pale blue flats. Her gemstone, a powder-blue pearl, is on her chest and is a round polished cabochon.
Blue Pearl was demure, humble, and quiet, choosing mainly to follow her Diamond's ways without much comment of her own. Much of her appearance had shown her in a calm demeanor and friendly sort, similar to Fluttershy, but a bit more soft-spoken.
However, after the first White Diamond incident, Blue began taking on more of her Mistress's personality traits. Perhaps most significantly, a curiousity towards Earth's ways. She even had an appreciation for aesthetic beauty, given how much she liked a Gem-influenced T-shirt once she found one in "Pearl's Day Out". She had also shown a bit more of a distraught however, and worry to her own diamond.
Throughout most of her appearances since her debut in Season 2, Blue Pearl has been seen accompanying her Diamond, and aiding her in whatever she could.
When she arrived to the Grand Galloping Gala, she learned a bit more about Rose Quartz from Pearl, and she began to feel a bit guilty for not being able to do much to stop her upcoming death, as she could've done something to help someone so caring. Pearl reassured her though that it wasn't her fault, and she returned to the gala with her.
In The Albino Diamond, Blue Pearl received perhaps the biggest shock of her life: While touring the White Diamond's Space Station, her Diamond was given a test in her loyalty by White Diamond ordering to shatter her own Pearl. However, to everyone's shock, Blue Diamond declared that she loved her pearl, something that was unheard of in the Homeworld Society. So touched she was by this, that when her diamond was poofed afterwards, she was distraught, not helped by her imprisonment afterwards. She was released though after a while, once Blue Diamond had reformed, and she returned with her Diamond to Homeworld.
Upon returning, Blue Pearl stayed by her diamond's side, trying her best to comfort her, even if it meant going back to Earth after being forbidden from going there.
During one point however, Blue Pearl became horrified when she discovered what remained of Grootslang's attack, and informed this immediately to the other remaining Diamonds, thus triggering The Trial to start. She herself didn't appear, but she was called up as a chief witness by Zircon. She explained what she knew, but couldn't finish her own sentence as it drove her to tears, and as such had to leave shortly afterwards.
When the others arrived back to Homeworld under Blue Diamond's order, Blue Pearl was the first to greet them, treating them as if they were her own diamond in terms of respect. When Pearlis arrived however, Blue Pearl silently got the team to move as Blue Diamond distracted her, giving them enough time to escape. Blue and Yellow Pearl were given a "vacation" to earth. While there, Blue got a first true look at what Earth was like without her diamond with her, being given a tour of Beach City by the Crystal Gems' Pearl escort. During one trip to the local library, she was the one who found the book on how gems were made, noting on the rarity of her diamond as the second-rarest diamond in the world, only behind Red Diamond.
While looking rather frail for a Gem, Blue Pearl has shown on one instance to be exceptionally strong, shown when she stopped Solitaire on the spot simply by grabbing his horns.