Mandos are usually blonde so that makes sense.
It appears the ethnicity of Mandos depends on their place of origin. Those coming from Mandalore itself look almost universally Caucasian with mostly blonde hair with a few redheads and brunettes. However Sabine and her relatives from clan Wren look ambiguously East Asian.
^ Jocasta actually has a canon appearance almost immediately after ROTS in Vader’s second comic book run, IIRC.
This is what inspired my headcanon in the first place. Jocasta is shown to be searching for ways to preserve the legacy of the Jedi Order and protect Force-sensitive infants.