Red Bloods are humans. Relationships with vampires include familiars (humans on which the Caeriomonia is performed) and Conduits (humans that serve and protect their vampires), though it is forbidden for the two occupations to be filled by the same Red Blood. Oliver Hazard-Perry broke this rule for Schuyler.
Some vampires respect Red Bloods, while others, like Mimi, hold them in disdain.
Vampires possess blue blood, or sangre azul, that carries their soul and allows them to have immortality through cycles of expression. Vampires can be called up through a process involving the blood.
To live, vampires must feed on human blood by performing the Caeriomonia Oscular, or Sacred Kiss. The human on which they perform the Kiss becomes their familiar. Both vampire and human feel a pull after the Kiss, but the human feels it more intensely. A human familiar that has been abandoned by their vampire may never feel right again.
Blue Bloods have the power to control Red Bloods to a point by using the glom, but they usually refrain from doing so because it can damage the Red Blood's mind. The glom can also be used as a spiritual realm in which spirits talk to each other, and to send messages between vampires, like how Schuyler would communicate with Lawrence in Rio or how she projected Mimi's memories for the Conclave during Mimi's trial.
Also called Abominations, Silver Bloods are Blue Bloods that have fed on other Blue Bloods rather humans. This makes them stronger, but can drive them insane, because the souls and memories contained in the blood are now in their body. The term Abomination describes the condition of multiple souls inhabiting one physical shell.
Bliss Llewellyn is a known Silver Blood.
Kingsley Martin is a "reformed" Silver Blood.