Hydroxylase involved in the biosynthesis pathway of the red naphthoquinone pigment shikonin (PubMed:30498024). Catalyzes the key step C-3''-hydroxylation of the prenylated phenolic intermediate geranylhydroquinone to form 3''-hydroxygeranylhydroquinone (PubMed:30498024). geranylhydroquinone + O2 + reduced [NADPH--hemoprotein reductase] = 3''-hydroxygeranylhydroquinone + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Belongs to the cytochrome P450 family.