oh dang, well fully explaining that would require unpacking a Whole Bunch of lore and introducing Bea and Clara's setting properly,
but for now here's the quick summery.
Bea is a genetic experiment created to be a sort of bio-weapon, she escaped however and now seeks to get revenge on and bring justice to her creators.
she conceals her face in order to hide this horrific origin ...and because she's embarrassed by the fact she's bright pink...