Emergency services such as the police, fire and ambulance staff who use blue flashing lights to either respond to an emergency call out or take someone to a hospital.
Gwasanaethau brys fel yr heddlu, staff tân ac ambiwlans sy’n defnyddio goleuadau glas sy’n fflachio i naill ai ymateb i alwad frys neu fynd â rhywun i ysbyty.