The yellow colour boosts the potency and energies invoked for the duration of Baglamukhi’s rituals and worship. It resonates with her intense nature and powers. This is without doubt one of the boons for which Bagalamukhi's devotees worship her. Other Mahavidya goddesses also are mentioned to signify identical powers handy https://www.youtube.com/watch?v=THS_mtzLsvE