Biryanis are grand, festive casseroles in which partially cooked rice is layered over cooked meat. Orange-coloured saffron milk is dribbled over the top, thereby colouring some grains yellow while leaving others white, then the dish is set to bake in a slow oven. As it cooks, the biryani becomes quite perfumed with saffron.
These days, with saffron being as expensive as it is, many people, even in India, use yellow food colouring as a substitute. You may also do so if you wish. Just